update models.py

change error handling to fix some issue and runtime error.

Author: hadikoub

src/main/models.py

@@ -8,5 +8,5 @@ def __init__(self, success=True, data=None, error=None):
         :param error: The error in case an exception was raised
         """
         self.data = data
-        self.error = error.get_message() if error is not None else ''
+        self.error = error.__str__() if error is not None else ''
         self.success = success