Cleanup exception printing for LabelboxError

Author: Val Brodsky

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):