Use multiline failure message for asser_raise/3

Before this commit, `assert_raise/3` in ExUnit used an uncomfortable
failure message when the expected exception message and the real one
didn't match: they were both written on the same line, which caused
problems for long-ish messages.

Now, each exception message is printed on its own line, which should
make it clearer to spot differences and cleaner in general.

Author: whatyouhide

lib/ex_unit/lib/ex_unit/assertions.ex

@@ -392,8 +392,11 @@ defmodule ExUnit.Assertions do
       Regex.regex?(message) -> Exception.message(error) =~ message
     end
 
-    msg = "Wrong message for #{inspect exception}. " <>
-          "Expected #{inspect message}, got #{inspect Exception.message(error)}"
+    msg = "Wrong message for #{inspect exception}\n" <>
+          "Expected:\n" <>
+          "  #{inspect message}\n" <>
+          "Got:\n" <>
+          "  #{inspect Exception.message(error)}"
     assert is_match, message: msg
 
     error