return error_description instead of error_message

Author: Sebastian Mennicke

src/pyop/exceptions.py

@@ -52,7 +52,7 @@ def to_error_url(self):
         redirect_uri = self.request.get('redirect_uri')
         response_type = self.request.get('response_type')
         if redirect_uri and response_type and self.oauth_error:
-            error_resp = AuthorizationErrorResponse(error=self.oauth_error, error_message=str(self),
+            error_resp = AuthorizationErrorResponse(error=self.oauth_error, error_description=str(self),
                                                     state=self.request.get('state'))
             return error_resp.request(redirect_uri, should_fragment_encode(self.request))