Python generic exception handling (#3473)

* update python wrapper to handle generic execptions, and return a SeldonMessage

* update branch

* formatting

python/seldon_core/wrapper.py

@@ -44,6 +44,16 @@ def get_rest_microservice(user_model, seldon_metrics):
         logger.info("Registering the custom error handler...")
         app.register_blueprint(user_model.model_error_handler)
 
+    @app.errorhandler(Exception)
+    def handle_generic_exception(e):
+        error = SeldonMicroserviceException(
+            message=str(e), status_code=500, reason="MICROSERVICE_INTERNAL_ERROR"
+        )
+        response = jsonify(error.to_dict())
+        logger.error("%s", error.to_dict())
+        response.status_code = error.status_code
+        return response
+
     @app.errorhandler(SeldonMicroserviceException)
     def handle_invalid_usage(error):
         response = jsonify(error.to_dict())