Make sure sorted_errors has unambiguous order for all error lists

Author: gazpachoking

tests.py

@@ -855,5 +855,5 @@ def test_it_catches_registered_errors(self):
 
 def sorted_errors(errors):
     def key(error):
-        return [str(e) for e in error.path], error.validator_keyword
+        return error.path, error.schema_path
     return sorted(errors, key=key)