Better exceptions

[pesterhazy]

The way unravel prints exceptions is hard to read

Using a plain clojure jar

user=> (/)
ExceptionInfo Exception during eval phase.  clojure.core$ex_info.invokeStatic (core.clj)
ArityException Wrong number of args (0) passed to: core//  clojure.lang.AFn.throwArity (AFn.java)
	clojure.lang.AFn.throwArity (AFn.java)
	clojure.lang.RestFn.invoke (RestFn.java)
	user$eval779.invokeStatic (unrepl-session)
	user$eval779.invoke (unrepl-session)
	clojure.lang.Compiler.eval (Compiler.java)
	clojure.lang.Compiler.eval (Compiler.java)
	clojure.core$eval.invokeStatic (core.clj)
	clojure.core$eval.invoke (core.clj)
	unrepl.replG__18$start$interruptible_eval__350$fn__351$fn__352$fn__353.invoke (NO_SOURCE_FILE)
	clojure.lang.AFn.applyToHelper (AFn.java)
	#__1

Using BOOT_VERSION=2.7.2-SNAPSHOT boot socket-server --port=50505 wait:

user=> (/)
#unrepl.java/class clojure.lang.ExceptionInfo Exception during eval phase.  (unknown)
#unrepl.java/class clojure.lang.ArityException Wrong number of args (0) passed to: core//  (unknown)
	#unrepl/object [#unrepl.java/class java.lang.StackTraceElement "0x5858e7a5" "clojure.lang.AFn.throwArity(AFn.java:429)" {:bean {#__22 #__23}}]
	#unrepl/object [#unrepl.java/class java.lang.StackTraceElement "0x64722719" "clojure.lang.RestFn.invoke(RestFn.java:399)" {:bean {#__24 #__25}}]
	#unrepl/object [#unrepl.java/class java.lang.StackTraceElement "0x658c7cd6" "user$eval919.invokeStatic(unrepl-session:5)" {:bean {#__26 #__27}}]
	#unrepl/object [#unrepl.java/class java.lang.StackTraceElement "0x17fed1ca" "user$eval919.invoke(unrepl-session:5)" {:bean {#__28 #__29}}]
	#unrepl/object [#unrepl.java/class java.lang.StackTraceElement "0x5ded34f6" "clojure.lang.Compiler.eval(Compiler.java:6927)" {:bean {#__30 #__31}}]
	#unrepl/object [#unrepl.java/class java.lang.StackTraceElement "0x3c6af889" "clojure.lang.Compiler.eval(Compiler.java:6890)" {:bean {#__32 #__33}}]
	#unrepl/object [#unrepl.java/class java.lang.StackTraceElement "0x476f4758" "clojure.core$eval.invokeStatic(core.clj:3105)" {:bean {#__34 #__35}}]
	#unrepl/object [#unrepl.java/class java.lang.StackTraceElement "0x448aaf55" "clojure.core$eval.invoke(core.clj:3101)" {:bean {#__36 #__37}}]
	#unrepl/object [#unrepl.java/class java.lang.StackTraceElement "0x64921c39" "unrepl.replG__51$start$interruptible_eval__375$fn__376$fn__377$fn__378.invoke(NO_SOURCE_FILE:495)" {:bean {#__38 #__39}}]
	#unrepl/object [#unrepl.java/class java.lang.StackTraceElement "0x4fd566bc" "clojure.lang.AFn.applyToHelper(AFn.java:152)" {:bean {#__40 #__41}}]
	#__42

Not sure why a server started by boot produces different exceptions.

In either case, exceptions should be printed in a more readable style, with long stack traces collapsed by default and a way to expand interactively.