Change task.error() to return None if 'error' doesn't exist

Author: Kevin Kim

labelbox/schema/task.py

@@ -75,7 +75,5 @@ def errors(self):
             response = requests.get(self.result)
             response.raise_for_status()
             data = response.json()
-            if 'error' not in data:
-                raise KeyError(f"Key 'error' does not exist in {data}")
-            return data['error']
+            return data.get('error')
         return None