Return 500 if a database error occurs

run_server.py

@@ -54,7 +54,7 @@ if __name__ == '__main__':
             print(e)
             model.connection.rollback()
             print('Processing time:', time.clock() - start)
-            return server_controller.bad_request('Action violates database constraints.')
+            return server_controller.internal_server_error('Action violates database constraints.')
 
 
     @route('/', method='GET')