diff --git a/Pipfile b/Pipfile
index 20d0e4a..064a730 100644
--- a/Pipfile
+++ b/Pipfile
@@ -9,7 +9,7 @@ numpy = "*"
 scipy = "*"
 biopython = "*"
 joblib = "*"
-pysam = "==0.15.3"
+pysam = "==0.15.4"
 requests = "*"
 
 [dev-packages]
diff --git a/Pipfile.lock b/Pipfile.lock
index 77c0cc2..738b8b0 100644
--- a/Pipfile.lock
+++ b/Pipfile.lock
@@ -1,7 +1,7 @@
 {
     "_meta": {
         "hash": {
-            "sha256": "b8caa5285498625db5153f6f2d146cf0f83fbe4cd13b337e8bf68bd38e0572e8"
+            "sha256": "c89fa10b0342cdd2da48682890ae5663b37e566d160c7aa1bb4fb823d31394b6"
         },
         "pipfile-spec": 6,
         "requires": {},
@@ -16,44 +16,41 @@
     "default": {
         "biopython": {
             "hashes": [
-                "sha256:015b79eea59bb5ccf7abef2ab17a813540c5c1969a8def2148fe3d529ff405a3",
-                "sha256:022909d10bbdfbc70eba6ea1c06ff573444e26e40ef0899025fb269898604b16",
-                "sha256:046510af3cbaaf822e7451f0772e3e3f327916edbfd1f34798e6b8cbf60e8aa3",
-                "sha256:1324bd2f6ea1dbad748085875d4c206f08748bb7848355f365d31fcd771dfa75",
-                "sha256:25152c1be2c9205bf80901fc49adf2c2efff49f0dddbcf6e6b2ce31dfa6590c0",
-                "sha256:273c524550aaad3284edbdacecdf66cfd880dac580a5f6c5f80a9925a70144fb",
-                "sha256:32c50dd9450ac780d640baa212ecde22fcc98dc0de472b40296968df2385c824",
-                "sha256:36c35d93d16c9270303bfc755d2364171a1aaebd75f3bfa97179712a3ac09e2d",
-                "sha256:3a802aba32b64aee9c3b92d8b5d50aa3d0a95c8188b69a78a2cbc292578dae08",
-                "sha256:540f9df15e11f091e2d92959b891d2001bb59660ca806d51ca30d76dab60d39e",
-                "sha256:6182f8c17c81aa40987b018e6241719137e463f5bb263c423db6180d118d3a03",
-                "sha256:67144db2defb3b49d505c7c4c676ca80b3451a0764f507b930b86031b7ebde5c",
-                "sha256:6d9a39f295d97ed953a48c1cde635b35205ed25034015238776dbd2a8afbb2a7",
-                "sha256:7103f3dd3cef9f6ae52c0c3275ecb65121f3935b90d25c5e149ce62f684fbaf2",
-                "sha256:77145b88a74c89f752db2ed11f64737161cc337c9e520e3853c945bd1d9866e6",
-                "sha256:7c32c37b20843e1d22e76c889f1733097e27996d1ec0fe54d84e5f737c9ff65e",
-                "sha256:8b7a3edd0dcc9eae3020849ad6110c721399f2c8dd71e54317dcc50035f9ebf9",
-                "sha256:a117596b366e2226e2bf0adaf87f32cda495357c398b1b2ca2ada9f54c386718",
-                "sha256:aa07bcf7def1c270c1fc1bab25f72a34f1ba24ab0a2d680f0a8466b39a2a7660",
-                "sha256:b8cdfaf2963b7ef24497aa82e60bfc86267989f32a49b4edd4a67aba75202834",
-                "sha256:bb302ad68a133ed3ae26efa0a0c82a0905c8b9b85a70fa6626611a882a65ec61",
-                "sha256:ca627475233f698ede17b5adb169ed10b44ab4dc3a48d71069d7ab0086bdbc1c",
-                "sha256:d3bf43ea45859bec05e8496c39dbd614c75520a832da20d826fdbd7e83105414",
-                "sha256:d6a310fab78e11dba51b55a2b194a79128d202584127e17952f7f64b52da83e2",
-                "sha256:e6cc6e725a5fb628d41ed675bb74aa5eb03763e1ccd3111d0f73f739c7263ab4",
-                "sha256:efee2f77cef1b65a76fe27af83c05774329b481c2da71d0580fcbcf92d6e9988",
-                "sha256:f50ee861a67e96488d21bc210ea72250df8cb7578351366f52c3904b841b5fbe",
-                "sha256:fa8ed2c3fec5dc45f9b750bd5da386f82cddb7944b456bfd0472106050efa397"
+                "sha256:01951f2474b9fbd38fa34678d2e3fab95497ea3ffa0a5570b2444dd3f906d730",
+                "sha256:0f3747f985e1890eb267752c4ef0163366a2232cbda4ff3b750dfd3b68e373dc",
+                "sha256:1d9f473ea96fa4eafa8dba5c1e0c2e98876a93a63a5b90a8eeda9b9192ad18d9",
+                "sha256:20550cad24f66d4c47be556464e892c3e7cadeadb83e28cd3118297dd4bc361b",
+                "sha256:3071a4d3e93baa316b3016039335d23d854e922335a6af96af58645d5c7ee676",
+                "sha256:3873cb98dad5e28d5e3f2215a012565345a398d3d2c4eebf7cd701757b828c72",
+                "sha256:45d91b68f65c1ec6f9bcae1b07bd836c2b99de612d1502a2f08d59502b77e5c6",
+                "sha256:4710fdaafdab18f20e5ff3e72732da4fe23c49e5bc0879c8cc07739cdd6b8088",
+                "sha256:526e01568d8ec12f161fb800e967ede2943bf1b61d44151bdc7e4242e58733ff",
+                "sha256:5f39d2ea4fb0d97fa2e3e8cb55f30dc82475cb95743e45779ffe2c2fd77ece5d",
+                "sha256:61bb0effa0252e3f296c49867f3303ecbb0f67d03730482141ff4b204a2b400c",
+                "sha256:628442d2cbdc0dfc04bd2f2cdc5d73712e2c30e6de4192f9cc6dc6badd3d8205",
+                "sha256:637795f150c15fdc122bef6798c4189c9f3c3a6f0d18bfbfaf3cc150fcdf6796",
+                "sha256:680b688ad6030b7efdd01eb2b9f0b3097b9ad509e9964597760a09dea5cdd5af",
+                "sha256:76a6bee1429e88eeaed4aa858bb9f656f44c79db40f726767659e4f95b2fcdb5",
+                "sha256:98c9b3e03233753cf5f3b6690a4be790f79a6ec290e2a578be1f0e2d982cf43b",
+                "sha256:aee7756947bc79cbcf5a9087ae34d0318f02d85fd5e1914e7fe3dddd4df93520",
+                "sha256:b1a29524cbea4eb7d6ef9c2626c8fdc3d21a1a0790b7a5a6725bfc57e129be39",
+                "sha256:b4d7f28c53884a9282ba3cc5e2887ae40ce2b4abfbb78cfb7a33bebe06a8c43a",
+                "sha256:d7cd8a169da9b44f878e218a51a494a7ccc5966a108f8607dcab360367fba6f3",
+                "sha256:e09d7ae93f93639d58d9314a47ccf8ee9fde4a9e36ba810cd0843b4afd1b1ddc",
+                "sha256:e3cad3ff77d19211430816e2bb5dd891b6a29f19e2441ef786979c42746c10b9",
+                "sha256:e75b9400aa6122f2c5af75111426a1a07f1ab078b47bd8ef0ff9ca6c54fd398e",
+                "sha256:f0c269d202c24fa1dc5afd4067320e1e9447904f31d0e7398b76c24e35fed35c",
+                "sha256:f5a14d4122b126f21e1d623a3e2e6723101840516fce15f225e69608dc023302"
             ],
             "index": "pypi",
-            "version": "==1.74"
+            "version": "==1.76"
         },
         "certifi": {
             "hashes": [
-                "sha256:e4f3620cfea4f83eedc95b24abd9cd56f3c4b146dd0177e83a21b4eb49e21e50",
-                "sha256:fd7c7c74727ddcf00e9acd26bba8da604ffec95bf1c2144e67aff7a8b50e6cef"
+                "sha256:1d987a998c75633c40847cc966fcf5904906c920a7f17ef374f5aa4282abd304",
+                "sha256:51fcb31174be6e6664c5f69e3e1691a2d72a1a12e90f872cbdb1567eb47b6519"
             ],
-            "version": "==2019.9.11"
+            "version": "==2020.4.5.1"
         },
         "chardet": {
             "hashes": [
@@ -64,105 +61,127 @@
         },
         "future": {
             "hashes": [
-                "sha256:858e38522e8fd0d3ce8f0c1feaf0603358e366d5403209674c7b617fa0c24093"
+                "sha256:b1bead90b70cf6ec3f0710ae53a525360fa360d306a86583adc6bf83a4db537d"
             ],
             "index": "pypi",
-            "version": "==0.18.1"
+            "version": "==0.18.2"
         },
         "idna": {
             "hashes": [
-                "sha256:c357b3f628cf53ae2c4c05627ecc484553142ca23264e593d327bcde5e9c3407",
-                "sha256:ea8b7f6188e6fa117537c3df7da9fc686d485087abf6ac197f9c46432f7e4a3c"
+                "sha256:7588d1c14ae4c77d74036e8c22ff447b26d0fde8f007354fd48a7814db15b7cb",
+                "sha256:a068a21ceac8a4d63dbfd964670474107f541babbd2250d61922f029858365fa"
             ],
-            "version": "==2.8"
+            "version": "==2.9"
         },
         "joblib": {
             "hashes": [
-                "sha256:006108c7576b3eb6c5b27761ddbf188eb6e6347696325ab2027ea1ee9a4b922d",
-                "sha256:6fcc57aacb4e89451fd449e9412687c51817c3f48662c3d8f38ba3f8a0a193ff"
+                "sha256:0630eea4f5664c463f23fbf5dcfc54a2bc6168902719fa8e19daf033022786c8",
+                "sha256:bdb4fd9b72915ffb49fde2229ce482dd7ae79d842ed8c2b4c932441495af1403"
             ],
             "index": "pypi",
-            "version": "==0.14.0"
+            "version": "==0.14.1"
         },
         "numpy": {
             "hashes": [
-                "sha256:0b0dd8f47fb177d00fa6ef2d58783c4f41ad3126b139c91dd2f7c4b3fdf5e9a5",
-                "sha256:25ffe71f96878e1da7e014467e19e7db90ae7d4e12affbc73101bcf61785214e",
-                "sha256:26efd7f7d755e6ca966a5c0ac5a930a87dbbaab1c51716ac26a38f42ecc9bc4b",
-                "sha256:28b1180c758abf34a5c3fea76fcee66a87def1656724c42bb14a6f9717a5bdf7",
-                "sha256:2e418f0a59473dac424f888dd57e85f77502a593b207809211c76e5396ae4f5c",
-                "sha256:30c84e3a62cfcb9e3066f25226e131451312a044f1fe2040e69ce792cb7de418",
-                "sha256:4650d94bb9c947151737ee022b934b7d9a845a7c76e476f3e460f09a0c8c6f39",
-                "sha256:4dd830a11e8724c9c9379feed1d1be43113f8bcce55f47ea7186d3946769ce26",
-                "sha256:4f2a2b279efde194877aff1f76cf61c68e840db242a5c7169f1ff0fd59a2b1e2",
-                "sha256:62d22566b3e3428dfc9ec972014c38ed9a4db4f8969c78f5414012ccd80a149e",
-                "sha256:669795516d62f38845c7033679c648903200980d68935baaa17ac5c7ae03ae0c",
-                "sha256:75fcd60d682db3e1f8fbe2b8b0c6761937ad56d01c1dc73edf4ef2748d5b6bc4",
-                "sha256:9395b0a41e8b7e9a284e3be7060db9d14ad80273841c952c83a5afc241d2bd98",
-                "sha256:9e37c35fc4e9410093b04a77d11a34c64bf658565e30df7cbe882056088a91c1",
-                "sha256:a0678793096205a4d784bd99f32803ba8100f639cf3b932dc63b21621390ea7e",
-                "sha256:b46554ad4dafb2927f88de5a1d207398c5385edbb5c84d30b3ef187c4a3894d8",
-                "sha256:c867eeccd934920a800f65c6068acdd6b87e80d45cd8c8beefff783b23cdc462",
-                "sha256:dd0667f5be56fb1b570154c2c0516a528e02d50da121bbbb2cbb0b6f87f59bc2",
-                "sha256:de2b1c20494bdf47f0160bd88ed05f5e48ae5dc336b8de7cfade71abcc95c0b9",
-                "sha256:f1df7b2b7740dd777571c732f98adb5aad5450aee32772f1b39249c8a50386f6",
-                "sha256:ffca69e29079f7880c5392bf675eb8b4146479d976ae1924d01cd92b04cccbcc"
+                "sha256:00d7b54c025601e28f468953d065b9b121ddca7fff30bed7be082d3656dd798d",
+                "sha256:02ec9582808c4e48be4e93cd629c855e644882faf704bc2bd6bbf58c08a2a897",
+                "sha256:0e6f72f7bb08f2f350ed4408bb7acdc0daba637e73bce9f5ea2b207039f3af88",
+                "sha256:1be2e96314a66f5f1ce7764274327fd4fb9da58584eaff00b5a5221edefee7d6",
+                "sha256:2466fbcf23711ebc5daa61d28ced319a6159b260a18839993d871096d66b93f7",
+                "sha256:2b573fcf6f9863ce746e4ad00ac18a948978bb3781cffa4305134d31801f3e26",
+                "sha256:3f0dae97e1126f529ebb66f3c63514a0f72a177b90d56e4bce8a0b5def34627a",
+                "sha256:50fb72bcbc2cf11e066579cb53c4ca8ac0227abb512b6cbc1faa02d1595a2a5d",
+                "sha256:57aea170fb23b1fd54fa537359d90d383d9bf5937ee54ae8045a723caa5e0961",
+                "sha256:709c2999b6bd36cdaf85cf888d8512da7433529f14a3689d6e37ab5242e7add5",
+                "sha256:7d59f21e43bbfd9a10953a7e26b35b6849d888fc5a331fa84a2d9c37bd9fe2a2",
+                "sha256:904b513ab8fbcbdb062bed1ce2f794ab20208a1b01ce9bd90776c6c7e7257032",
+                "sha256:96dd36f5cdde152fd6977d1bbc0f0561bccffecfde63cd397c8e6033eb66baba",
+                "sha256:9933b81fecbe935e6a7dc89cbd2b99fea1bf362f2790daf9422a7bb1dc3c3085",
+                "sha256:bbcc85aaf4cd84ba057decaead058f43191cc0e30d6bc5d44fe336dc3d3f4509",
+                "sha256:dccd380d8e025c867ddcb2f84b439722cf1f23f3a319381eac45fd077dee7170",
+                "sha256:e22cd0f72fc931d6abc69dc7764484ee20c6a60b0d0fee9ce0426029b1c1bdae",
+                "sha256:ed722aefb0ebffd10b32e67f48e8ac4c5c4cf5d3a785024fdf0e9eb17529cd9d",
+                "sha256:efb7ac5572c9a57159cf92c508aad9f856f1cb8e8302d7fdb99061dbe52d712c",
+                "sha256:efdba339fffb0e80fcc19524e4fdbda2e2b5772ea46720c44eaac28096d60720",
+                "sha256:f22273dd6a403ed870207b853a856ff6327d5cbce7a835dfa0645b3fc00273ec"
             ],
             "index": "pypi",
-            "version": "==1.17.3"
+            "version": "==1.18.4"
         },
         "pysam": {
             "hashes": [
-                "sha256:a98dd0a164aa664b1ab30a36f653752f00e93c13deeb66868597f4b2a30f7265"
+                "sha256:00a1f62e704410343ef6a6232f5bdd29f67f88326a89757e665dee035ef36112",
+                "sha256:00c7f094be02ba8daf2feb51467b70142f9cca22fb5336b504bc58568a2500de",
+                "sha256:0b0f407ad96b3bd492017ee82a317ac0fc68dc858ecba9119e4ae69b1cda9910",
+                "sha256:0f3e42cbc9bac07cf6a880c2ae318c24aea20f43a3f3562e53068266627cb7a7",
+                "sha256:179e68c5acb8cc6a79a79441ba6cffb88d7c3afb74c7b170395c248cb7b9f138",
+                "sha256:2581ab403fdba02e2261cf2f9df783f24de5530e1f77c84236707f8d8706cd91",
+                "sha256:28fd770354ecf621ee47425bfdcf012097fa7a8ff590b49ec953d059221886c2",
+                "sha256:333e9e73addb0579aa8af08c6618b359bd038a3710428b7ce1caef0075392b3c",
+                "sha256:3d5158231cab88cb8a931b78f34fb6eb939a093cb8d5273452cc12d3206e445e",
+                "sha256:495815ef466aefa80d949ac449cd364f21cb20ee56b1a0bd623352ad3f73bf14",
+                "sha256:4ddcb84e471aff2f55beb5ed2d368dc6e773947c628a1a7b6d5ceec9c141ce51",
+                "sha256:5a9730d9775dc30a8cc197ca3e5340b7c3cb63b66c387ecfd8e665426f083f65",
+                "sha256:5b6a2258e326204ee94bf4d482d9a137ce8cbb3f3cefada42c7f26802d15b95d",
+                "sha256:5bcf5d49922aeaccd0dbf0b3e4327b03be2883814bf2476e83f20fc24d7be02b",
+                "sha256:62b72de5af5b8550f376a580fecb23b81d989140cf95f8465fef2c3d96006424",
+                "sha256:7c358f69620e7b9af7548a62ca2a1fb6b51c03fcdc79a0ca8d1839ad92a532ce",
+                "sha256:a535e15cbd6e27f4ab74cabca30ca1df7eea283cb91d3b536d47fe113fee066f",
+                "sha256:d9f116b2e32b678bbd95ba0c83a449d0a59f2deb04a6fc02f42b5cd9e406bde5"
             ],
             "index": "pypi",
-            "version": "==0.15.3"
+            "version": "==0.15.4"
         },
         "requests": {
             "hashes": [
-                "sha256:11e007a8a2aa0323f5a921e9e6a2d7e4e67d9877e85773fba9ba6419025cbeb4",
-                "sha256:9cf5292fcd0f598c671cfc1e0d7d1a7f13bb8085e9a590f48c010551dc6c4b31"
+                "sha256:43999036bfa82904b6af1d99e4882b560e5e2c68e5c4b0aa03b655f3d7d73fee",
+                "sha256:b3f43d496c6daba4493e7c431722aeb7dbc6288f52a6e04e7b6023b0247817e6"
             ],
             "index": "pypi",
-            "version": "==2.22.0"
+            "version": "==2.23.0"
         },
         "scipy": {
             "hashes": [
-                "sha256:0baa64bf42592032f6f6445a07144e355ca876b177f47ad8d0612901c9375bef",
-                "sha256:243b04730d7223d2b844bda9500310eecc9eda0cba9ceaf0cde1839f8287dfa8",
-                "sha256:2643cfb46d97b7797d1dbdb6f3c23fe3402904e3c90e6facfe6a9b98d808c1b5",
-                "sha256:396eb4cdad421f846a1498299474f0a3752921229388f91f60dc3eda55a00488",
-                "sha256:3ae3692616975d3c10aca6d574d6b4ff95568768d4525f76222fb60f142075b9",
-                "sha256:435d19f80b4dcf67dc090cc04fde2c5c8a70b3372e64f6a9c58c5b806abfa5a8",
-                "sha256:46a5e55850cfe02332998b3aef481d33f1efee1960fe6cfee0202c7dd6fc21ab",
-                "sha256:75b513c462e58eeca82b22fc00f0d1875a37b12913eee9d979233349fce5c8b2",
-                "sha256:7ccfa44a08226825126c4ef0027aa46a38c928a10f0a8a8483c80dd9f9a0ad44",
-                "sha256:89dd6a6d329e3f693d1204d5562dd63af0fd7a17854ced17f9cbc37d5b853c8d",
-                "sha256:a81da2fe32f4eab8b60d56ad43e44d93d392da228a77e229e59b51508a00299c",
-                "sha256:a9d606d11eb2eec7ef893eb825017fbb6eef1e1d0b98a5b7fc11446ebeb2b9b1",
-                "sha256:ac37eb652248e2d7cbbfd89619dce5ecfd27d657e714ed049d82f19b162e8d45",
-                "sha256:cbc0611699e420774e945f6a4e2830f7ca2b3ee3483fca1aa659100049487dd5",
-                "sha256:d02d813ec9958ed63b390ded463163685af6025cb2e9a226ec2c477df90c6957",
-                "sha256:dd3b52e00f93fd1c86f2d78243dfb0d02743c94dd1d34ffea10055438e63b99d"
+                "sha256:00af72998a46c25bdb5824d2b729e7dabec0c765f9deb0b504f928591f5ff9d4",
+                "sha256:0902a620a381f101e184a958459b36d3ee50f5effd186db76e131cbefcbb96f7",
+                "sha256:1e3190466d669d658233e8a583b854f6386dd62d655539b77b3fa25bfb2abb70",
+                "sha256:2cce3f9847a1a51019e8c5b47620da93950e58ebc611f13e0d11f4980ca5fecb",
+                "sha256:3092857f36b690a321a662fe5496cb816a7f4eecd875e1d36793d92d3f884073",
+                "sha256:386086e2972ed2db17cebf88610aab7d7f6e2c0ca30042dc9a89cf18dcc363fa",
+                "sha256:71eb180f22c49066f25d6df16f8709f215723317cc951d99e54dc88020ea57be",
+                "sha256:770254a280d741dd3436919d47e35712fb081a6ff8bafc0f319382b954b77802",
+                "sha256:787cc50cab3020a865640aba3485e9fbd161d4d3b0d03a967df1a2881320512d",
+                "sha256:8a07760d5c7f3a92e440ad3aedcc98891e915ce857664282ae3c0220f3301eb6",
+                "sha256:8d3bc3993b8e4be7eade6dcc6fd59a412d96d3a33fa42b0fa45dc9e24495ede9",
+                "sha256:9508a7c628a165c2c835f2497837bf6ac80eb25291055f56c129df3c943cbaf8",
+                "sha256:a144811318853a23d32a07bc7fd5561ff0cac5da643d96ed94a4ffe967d89672",
+                "sha256:a1aae70d52d0b074d8121333bc807a485f9f1e6a69742010b33780df2e60cfe0",
+                "sha256:a2d6df9eb074af7f08866598e4ef068a2b310d98f87dc23bd1b90ec7bdcec802",
+                "sha256:bb517872058a1f087c4528e7429b4a44533a902644987e7b2fe35ecc223bc408",
+                "sha256:c5cac0c0387272ee0e789e94a570ac51deb01c796b37fb2aad1fb13f85e2f97d",
+                "sha256:cc971a82ea1170e677443108703a2ec9ff0f70752258d0e9f5433d00dda01f59",
+                "sha256:dba8306f6da99e37ea08c08fef6e274b5bf8567bb094d1dbe86a20e532aca088",
+                "sha256:dc60bb302f48acf6da8ca4444cfa17d52c63c5415302a9ee77b3b21618090521",
+                "sha256:dee1bbf3a6c8f73b6b218cb28eed8dd13347ea2f87d572ce19b289d6fd3fbc59"
             ],
             "index": "pypi",
-            "version": "==1.3.1"
+            "version": "==1.4.1"
         },
         "urllib3": {
             "hashes": [
-                "sha256:3de946ffbed6e6746608990594d08faac602528ac7015ac28d33cee6a45b7398",
-                "sha256:9a107b99a5393caf59c7aa3c1249c16e6879447533d0887f4336dde834c7be86"
+                "sha256:3018294ebefce6572a474f0604c2021e33b3fd8006ecd11d62107a5d2a963527",
+                "sha256:88206b0eb87e6d677d424843ac5209e3fb9d0190d0ee169599165ec25e9d9115"
             ],
-            "version": "==1.25.6"
+            "version": "==1.25.9"
         }
     },
     "develop": {
         "certifi": {
             "hashes": [
-                "sha256:e4f3620cfea4f83eedc95b24abd9cd56f3c4b146dd0177e83a21b4eb49e21e50",
-                "sha256:fd7c7c74727ddcf00e9acd26bba8da604ffec95bf1c2144e67aff7a8b50e6cef"
+                "sha256:1d987a998c75633c40847cc966fcf5904906c920a7f17ef374f5aa4282abd304",
+                "sha256:51fcb31174be6e6664c5f69e3e1691a2d72a1a12e90f872cbdb1567eb47b6519"
             ],
-            "version": "==2019.9.11"
+            "version": "==2020.4.5.1"
         },
         "chardet": {
             "hashes": [
@@ -173,55 +192,54 @@
         },
         "codecov": {
             "hashes": [
-                "sha256:8ed8b7c6791010d359baed66f84f061bba5bd41174bf324c31311e8737602788",
-                "sha256:ae00d68e18d8a20e9c3288ba3875ae03db3a8e892115bf9b83ef20507732bed4"
+                "sha256:09fb045eb044a619cd2b9dacd7789ae8e322cb7f18196378579fd8d883e6b665",
+                "sha256:aeeefa3a03cac8a78e4f988e935b51a4689bb1f17f20d4e827807ee11135f845"
             ],
             "index": "pypi",
-            "version": "==2.0.15"
+            "version": "==2.0.22"
         },
         "coverage": {
             "hashes": [
-                "sha256:08907593569fe59baca0bf152c43f3863201efb6113ecb38ce7e97ce339805a6",
-                "sha256:0be0f1ed45fc0c185cfd4ecc19a1d6532d72f86a2bac9de7e24541febad72650",
-                "sha256:141f08ed3c4b1847015e2cd62ec06d35e67a3ac185c26f7635f4406b90afa9c5",
-                "sha256:19e4df788a0581238e9390c85a7a09af39c7b539b29f25c89209e6c3e371270d",
-                "sha256:23cc09ed395b03424d1ae30dcc292615c1372bfba7141eb85e11e50efaa6b351",
-                "sha256:245388cda02af78276b479f299bbf3783ef0a6a6273037d7c60dc73b8d8d7755",
-                "sha256:331cb5115673a20fb131dadd22f5bcaf7677ef758741312bee4937d71a14b2ef",
-                "sha256:386e2e4090f0bc5df274e720105c342263423e77ee8826002dcffe0c9533dbca",
-                "sha256:3a794ce50daee01c74a494919d5ebdc23d58873747fa0e288318728533a3e1ca",
-                "sha256:60851187677b24c6085248f0a0b9b98d49cba7ecc7ec60ba6b9d2e5574ac1ee9",
-                "sha256:63a9a5fc43b58735f65ed63d2cf43508f462dc49857da70b8980ad78d41d52fc",
-                "sha256:6b62544bb68106e3f00b21c8930e83e584fdca005d4fffd29bb39fb3ffa03cb5",
-                "sha256:6ba744056423ef8d450cf627289166da65903885272055fb4b5e113137cfa14f",
-                "sha256:7494b0b0274c5072bddbfd5b4a6c6f18fbbe1ab1d22a41e99cd2d00c8f96ecfe",
-                "sha256:826f32b9547c8091679ff292a82aca9c7b9650f9fda3e2ca6bf2ac905b7ce888",
-                "sha256:93715dffbcd0678057f947f496484e906bf9509f5c1c38fc9ba3922893cda5f5",
-                "sha256:9a334d6c83dfeadae576b4d633a71620d40d1c379129d587faa42ee3e2a85cce",
-                "sha256:af7ed8a8aa6957aac47b4268631fa1df984643f07ef00acd374e456364b373f5",
-                "sha256:bf0a7aed7f5521c7ca67febd57db473af4762b9622254291fbcbb8cd0ba5e33e",
-                "sha256:bf1ef9eb901113a9805287e090452c05547578eaab1b62e4ad456fcc049a9b7e",
-                "sha256:c0afd27bc0e307a1ffc04ca5ec010a290e49e3afbe841c5cafc5c5a80ecd81c9",
-                "sha256:dd579709a87092c6dbee09d1b7cfa81831040705ffa12a1b248935274aee0437",
-                "sha256:df6712284b2e44a065097846488f66840445eb987eb81b3cc6e4149e7b6982e1",
-                "sha256:e07d9f1a23e9e93ab5c62902833bf3e4b1f65502927379148b6622686223125c",
-                "sha256:e2ede7c1d45e65e209d6093b762e98e8318ddeff95317d07a27a2140b80cfd24",
-                "sha256:e4ef9c164eb55123c62411f5936b5c2e521b12356037b6e1c2617cef45523d47",
-                "sha256:eca2b7343524e7ba246cab8ff00cab47a2d6d54ada3b02772e908a45675722e2",
-                "sha256:eee64c616adeff7db37cc37da4180a3a5b6177f5c46b187894e633f088fb5b28",
-                "sha256:ef824cad1f980d27f26166f86856efe11eff9912c4fed97d3804820d43fa550c",
-                "sha256:efc89291bd5a08855829a3c522df16d856455297cf35ae827a37edac45f466a7",
-                "sha256:fa964bae817babece5aa2e8c1af841bebb6d0b9add8e637548809d040443fee0",
-                "sha256:ff37757e068ae606659c28c3bd0d923f9d29a85de79bf25b2b34b148473b5025"
+                "sha256:00f1d23f4336efc3b311ed0d807feb45098fc86dee1ca13b3d6768cdab187c8a",
+                "sha256:01333e1bd22c59713ba8a79f088b3955946e293114479bbfc2e37d522be03355",
+                "sha256:0cb4be7e784dcdc050fc58ef05b71aa8e89b7e6636b99967fadbdba694cf2b65",
+                "sha256:0e61d9803d5851849c24f78227939c701ced6704f337cad0a91e0972c51c1ee7",
+                "sha256:1601e480b9b99697a570cea7ef749e88123c04b92d84cedaa01e117436b4a0a9",
+                "sha256:2742c7515b9eb368718cd091bad1a1b44135cc72468c731302b3d641895b83d1",
+                "sha256:2d27a3f742c98e5c6b461ee6ef7287400a1956c11421eb574d843d9ec1f772f0",
+                "sha256:402e1744733df483b93abbf209283898e9f0d67470707e3c7516d84f48524f55",
+                "sha256:5c542d1e62eece33c306d66fe0a5c4f7f7b3c08fecc46ead86d7916684b36d6c",
+                "sha256:5f2294dbf7875b991c381e3d5af2bcc3494d836affa52b809c91697449d0eda6",
+                "sha256:6402bd2fdedabbdb63a316308142597534ea8e1895f4e7d8bf7476c5e8751fef",
+                "sha256:66460ab1599d3cf894bb6baee8c684788819b71a5dc1e8fa2ecc152e5d752019",
+                "sha256:782caea581a6e9ff75eccda79287daefd1d2631cc09d642b6ee2d6da21fc0a4e",
+                "sha256:79a3cfd6346ce6c13145731d39db47b7a7b859c0272f02cdb89a3bdcbae233a0",
+                "sha256:7a5bdad4edec57b5fb8dae7d3ee58622d626fd3a0be0dfceda162a7035885ecf",
+                "sha256:8fa0cbc7ecad630e5b0f4f35b0f6ad419246b02bc750de7ac66db92667996d24",
+                "sha256:a027ef0492ede1e03a8054e3c37b8def89a1e3c471482e9f046906ba4f2aafd2",
+                "sha256:a3f3654d5734a3ece152636aad89f58afc9213c6520062db3978239db122f03c",
+                "sha256:a82b92b04a23d3c8a581fc049228bafde988abacba397d57ce95fe95e0338ab4",
+                "sha256:acf3763ed01af8410fc36afea23707d4ea58ba7e86a8ee915dfb9ceff9ef69d0",
+                "sha256:adeb4c5b608574a3d647011af36f7586811a2c1197c861aedb548dd2453b41cd",
+                "sha256:b83835506dfc185a319031cf853fa4bb1b3974b1f913f5bb1a0f3d98bdcded04",
+                "sha256:bb28a7245de68bf29f6fb199545d072d1036a1917dca17a1e75bbb919e14ee8e",
+                "sha256:bf9cb9a9fd8891e7efd2d44deb24b86d647394b9705b744ff6f8261e6f29a730",
+                "sha256:c317eaf5ff46a34305b202e73404f55f7389ef834b8dbf4da09b9b9b37f76dd2",
+                "sha256:dbe8c6ae7534b5b024296464f387d57c13caa942f6d8e6e0346f27e509f0f768",
+                "sha256:de807ae933cfb7f0c7d9d981a053772452217df2bf38e7e6267c9cbf9545a796",
+                "sha256:dead2ddede4c7ba6cb3a721870f5141c97dc7d85a079edb4bd8d88c3ad5b20c7",
+                "sha256:dec5202bfe6f672d4511086e125db035a52b00f1648d6407cc8e526912c0353a",
+                "sha256:e1ea316102ea1e1770724db01998d1603ed921c54a86a2efcb03428d5417e489",
+                "sha256:f90bfc4ad18450c80b024036eaf91e4a246ae287701aaa88eaebebf150868052"
             ],
-            "version": "==4.5.4"
+            "version": "==5.1"
         },
         "idna": {
             "hashes": [
-                "sha256:c357b3f628cf53ae2c4c05627ecc484553142ca23264e593d327bcde5e9c3407",
-                "sha256:ea8b7f6188e6fa117537c3df7da9fc686d485087abf6ac197f9c46432f7e4a3c"
+                "sha256:7588d1c14ae4c77d74036e8c22ff447b26d0fde8f007354fd48a7814db15b7cb",
+                "sha256:a068a21ceac8a4d63dbfd964670474107f541babbd2250d61922f029858365fa"
             ],
-            "version": "==2.8"
+            "version": "==2.9"
         },
         "nose": {
             "hashes": [
@@ -242,26 +260,26 @@
         },
         "pycodestyle": {
             "hashes": [
-                "sha256:95a2219d12372f05704562a14ec30bc76b05a5b297b21a5dfe3f6fac3491ae56",
-                "sha256:e40a936c9a450ad81df37f549d676d127b1b66000a6c500caa2b085bc0ca976c"
+                "sha256:2295e7b2f6b5bd100585ebcb1f616591b652db8a741695b3d8f5d28bdc934367",
+                "sha256:c58a7d2815e0e8d7972bf1803331fb0152f867bd89adf8a01dfd55085434192e"
             ],
             "index": "pypi",
-            "version": "==2.5.0"
+            "version": "==2.6.0"
         },
         "requests": {
             "hashes": [
-                "sha256:11e007a8a2aa0323f5a921e9e6a2d7e4e67d9877e85773fba9ba6419025cbeb4",
-                "sha256:9cf5292fcd0f598c671cfc1e0d7d1a7f13bb8085e9a590f48c010551dc6c4b31"
+                "sha256:43999036bfa82904b6af1d99e4882b560e5e2c68e5c4b0aa03b655f3d7d73fee",
+                "sha256:b3f43d496c6daba4493e7c431722aeb7dbc6288f52a6e04e7b6023b0247817e6"
             ],
             "index": "pypi",
-            "version": "==2.22.0"
+            "version": "==2.23.0"
         },
         "urllib3": {
             "hashes": [
-                "sha256:3de946ffbed6e6746608990594d08faac602528ac7015ac28d33cee6a45b7398",
-                "sha256:9a107b99a5393caf59c7aa3c1249c16e6879447533d0887f4336dde834c7be86"
+                "sha256:3018294ebefce6572a474f0604c2021e33b3fd8006ecd11d62107a5d2a963527",
+                "sha256:88206b0eb87e6d677d424843ac5209e3fb9d0190d0ee169599165ec25e9d9115"
             ],
-            "version": "==1.25.6"
+            "version": "==1.25.9"
         }
     }
 }
diff --git a/iss/download.py b/iss/download.py
index f6e16c1..08d0242 100644
--- a/iss/download.py
+++ b/iss/download.py
@@ -5,14 +5,23 @@
 from Bio import Entrez
 
 import io
+import sys
+import time
 import zlib
 import random
 import logging
 
-
 import requests
 
 
+class BadRequestError(Exception):
+    """Exception to raise when a http request does not return 200
+    """
+
+    def __init__(self, url, status_code):
+        super().__init__('%s returned %d' % (url, status_code))
+
+
 def ncbi(kingdom, n_genomes, output):
     """download random genomes sequences from ncbi genomes with entrez eutils
         and requests.
@@ -32,7 +41,6 @@ def ncbi(kingdom, n_genomes, output):
         'assembly',
         term='%s[Organism] AND "latest refseq"[filter] AND "complete genome"[filter]'
         % kingdom, retmax=100000))['IdList']
-    genomes = []
     n = 0
     logger.info('Searching for %s to download' % kingdom)
     while n < n_genomes:
@@ -48,8 +56,16 @@ def ncbi(kingdom, n_genomes, output):
                    genome_info['AssemblyAccession'],
                    genome_info['AssemblyName'])
             logger.info('Downloading %s' % genome_info['AssemblyAccession'])
-            assembly_to_fasta(url, output)
-            n += 1
+            try:
+                assembly_to_fasta(url, output)
+            except BadRequestError as e:
+                logger.debug('Could not download %s' %
+                             genome_info['AssemblyAccession'])
+                logger.debug('Skipping and waiting two seconds')
+                time.sleep(2)
+            else:
+                n += 1
+                full_id_list.remove(ident)
     return output
 
 
@@ -71,8 +87,11 @@ def assembly_to_fasta(url, output, chunk_size=1024):
         url = url.replace("ftp://", "https://")
     if url:
         request = requests.get(url)
-        request = zlib.decompress(
-            request.content, zlib.MAX_WBITS | 32).decode()
+        if request.status_code == 200:
+            request = zlib.decompress(
+                request.content, zlib.MAX_WBITS | 32).decode()
+        else:
+            raise BadRequestError(url, request.status_code)
 
     with io.StringIO(request) as fasta_io:
         seq_handle = SeqIO.parse(fasta_io, 'fasta')
diff --git a/iss/error_models/kde.py b/iss/error_models/kde.py
index 84ee72b..93cb5dc 100644
--- a/iss/error_models/kde.py
+++ b/iss/error_models/kde.py
@@ -29,6 +29,7 @@ class KDErrorModel(ErrorModel):
     - the substitution for each nucleotide at each position (for R1 and R2)
     - the insertion and deletion rates for each position (for R1 and R2)
     """
+
     def __init__(self, npz_path):
         super().__init__()
         self.npz_path = npz_path
@@ -74,7 +75,8 @@ def gen_phred_scores(self, cdfs, orientation):
             mean = self.mean_reverse
 
         norm_mean = mean / sum(mean)
-        quality_bin = np.searchsorted(norm_mean, np.random.rand())
+        # quality_bin = np.searchsorted(norm_mean, np.random.rand())
+        quality_bin = np.random.choice(range(len(norm_mean)), p=norm_mean)
         # downgrades index out of bound (ex rand is 1, last bin in searchsorted
         # is 0.95) to best quality bin
         if quality_bin == 4:
diff --git a/iss/generator.py b/iss/generator.py
index 5d7b407..70a6c36 100644
--- a/iss/generator.py
+++ b/iss/generator.py
@@ -62,21 +62,30 @@ def reads(record, ErrorModel, n_pairs, cpu_number, output, seed,
         # except ValueError as e:
         #     logger.error('Skipping this record: %s' % record.id)
         #     return
-        forward, reverse = simulate_read(record, ErrorModel, i, cpu_number)
-        if gc_bias:
-            stiched_seq = forward.seq + reverse.seq
-            gc_content = GC(stiched_seq)
-            if 40 < gc_content < 60:
-                read_tuple_list.append((forward, reverse))
-                i += 1
-            elif np.random.rand() < 0.90:
+        try:
+            forward, reverse = simulate_read(record, ErrorModel, i, cpu_number)
+        except AssertionError as e:
+            logger.warning(
+                '%s shorter than read length for this ErrorModel' % record.id)
+            logger.warning(
+                'Skipping %s. You will have less reads than specified'
+                % record.id)
+            break
+        else:
+            if gc_bias:
+                stiched_seq = forward.seq + reverse.seq
+                gc_content = GC(stiched_seq)
+                if 40 < gc_content < 60:
+                    read_tuple_list.append((forward, reverse))
+                    i += 1
+                elif np.random.rand() < 0.90:
+                    read_tuple_list.append((forward, reverse))
+                    i += 1
+                else:
+                    continue
+            else:
                 read_tuple_list.append((forward, reverse))
                 i += 1
-            else:
-                continue
-        else:
-            read_tuple_list.append((forward, reverse))
-            i += 1
 
     temp_file_name = output + '.iss.tmp.%s.%s' % (record.id, cpu_number)
     to_fastq(read_tuple_list, temp_file_name)
@@ -112,10 +121,7 @@ def simulate_read(record, ErrorModel, i, cpu_number):
         forward_start = random.randrange(
             0, len(record.seq) - (2 * read_length + insert_size))
     except AssertionError as e:
-        logger.error(
-            '%s shorter than read length for this ErrorModel:%s'
-            % (e, record.id))
-        sys.exit(1)
+        raise
     except ValueError as e:
         logger.debug(
             '%s shorter than template length for this ErrorModel:%s'
diff --git a/iss/test/test_generator.py b/iss/test/test_generator.py
index 4c76bfb..0a7c7d2 100644
--- a/iss/test/test_generator.py
+++ b/iss/test/test_generator.py
@@ -61,7 +61,7 @@ def test_simulate_and_save_short():
     generator.reads(ref_genome, err_mod, 1000, 0, 'data/.test', 0, True)
 
 
-@raises(SystemExit)
+@raises(AssertionError)
 def test_small_input():
     err_mod = kde.KDErrorModel('data/ecoli.npz')
     ref_genome = SeqRecord(
diff --git a/iss/version.py b/iss/version.py
index 5e235ea..adf1ed5 100644
--- a/iss/version.py
+++ b/iss/version.py
@@ -1 +1 @@
-__version__ = '1.4.5'
+__version__ = '1.4.6'