Support modern repr of BaseException

BaseException doesn't add trailing comma from version 3.7.0.
Hence the test case without ',' is added as well.

See also: https://bugs.python.org/issue30399

Author: shiplu

tests/test_server.py

@@ -215,7 +215,7 @@ class MySrv(zerorpc.Server):
     assert event.name == 'ERR'
     (msg,) = event.args
     print('msg only', msg)
-    assert msg == "NameError('donotexist',)"
+    assert msg in ("NameError('donotexist',)", "NameError('donotexist')")
 
     client_events.close()
     srv.close()