Do not include 'extensions' in validation condition

as it is an optional field

Author: extrin

gql/transport/aiohttp.py

@@ -228,11 +228,7 @@ async def execute(
                     f"Server did not return a GraphQL result: {result_text}"
                 )
 
-            if (
-                "errors" not in result
-                and "data" not in result
-                and "extensions" not in result
-            ):
+            if "errors" not in result and "data" not in result:
                 result_text = await resp.text()
                 raise TransportProtocolError(
                     "Server did not return a GraphQL result: "

gql/transport/requests.py

@@ -168,11 +168,7 @@ def execute(  # type: ignore
 
             raise TransportProtocolError("Server did not return a GraphQL result")
 
-        if (
-            "errors" not in result
-            and "data" not in result
-            and "extensions" not in result
-        ):
+        if "errors" not in result and "data" not in result:
             raise TransportProtocolError("Server did not return a GraphQL result")
 
         return ExecutionResult(

gql/transport/websockets.py

@@ -297,14 +297,9 @@ def _parse_answer(
 
                     if answer_type == "data":
 
-                        if (
-                            "errors" not in payload
-                            and "data" not in payload
-                            and "extensions" not in payload
-                        ):
+                        if "errors" not in payload and "data" not in payload:
                             raise ValueError(
-                                "payload does not contain 'data' or 'errors' "
-                                "or 'extensions' fields"
+                                "payload does not contain 'data' or 'errors' fields"
                             )
 
                         execution_result = ExecutionResult(