CPython 3.7 changed exception’s repr implementation to get rid of a trailing comma:

repr for BaseException has changed to not include the trailing comma. Most exceptions are affected by this change. (Contributed by Serhiy Storchaka in bpo-30399.)

This makes the test case from exceptions.py fail on CPython 3.7 and later.

Should we get rid of the tests for repr, or perhaps just test substrings (that repr string contains both the type and the message)?