Cleanup exception printing for LabelboxError

Author: Val Brodsky

libs/labelbox/src/labelbox/client.py

@@ -148,7 +148,7 @@ def execute(
         experimental=False,
         error_log_key="message",
         raise_return_resource_not_found=False,
-        error_handlers: Optional[Dict[str, Callable[[Dict[str, Any]],
+        error_handlers: Optional[Dict[str, Callable[[requests.models.Response],
                                                     None]]] = None
     ) -> Dict[str, Any]:
         """ Sends a request to the server for the execution of the

libs/labelbox/src/labelbox/exceptions.py

@@ -16,7 +16,10 @@ def __init__(self, message, cause=None):
         self.cause = cause
 
     def __str__(self):
-        return self.message + str(self.args)
+        exception_message = self.message
+        if self.cause is not None:
+            exception_message += " (caused by: %s)" % self.cause
+        return exception_message
 
 
 class AuthenticationError(LabelboxError):