check version bump on library modifications (#448)

* check version bump on library modifications

* add env to whitelist

* add extra space for gh

* address PR comments

tox.ini

@@ -73,9 +73,14 @@ deps =
     integration: pytest-operator==1.0.0b1
 commands =
     charm: mypy {[vars]src_path} {posargs}
-    lib: mypy --python-version 3.5 {[vars]lib_path} {posargs}
+    lib: mypy --python-version 3.8 {[vars]lib_path} {posargs}
+      /usr/bin/env sh -c 'for m in $(git diff --name-only {[vars]lib_path}); do \
+        if ! git diff $m | grep -q "+LIBPATCH\|+LIBAPI"; then \
+          echo "You forgot to bump the version on $m!"; exit 1; \
+        fi; done'
     unit: mypy {[vars]tst_path}/unit {posargs}
     integration: mypy {[vars]tst_path}/integration {posargs}
+allowlist_externals = /usr/bin/env
 
 [testenv:unit]
 description = Run unit tests