Update mypy/errorcodes.py: add category there

Author: wyattscarpenter

mypy/errorcodes.py

@@ -39,7 +39,7 @@ def __str__(self) -> str:
 
     def __repr__(self) -> str:
         """This doesn't fulfill the goals of repr but it's better than the default view."""
-        return f"<ErrorCode {self.code}>"
+        return f"<ErrorCode {self.category}: {self.code}>"
 
     def __eq__(self, other: object) -> bool:
         if not isinstance(other, ErrorCode):