Allow 400 status code if result contain valid graphql error message

[koliyo]

The graphql server I am using return a HTTP 400 response for invalid requests. So I get both a 400 response, but with proper graphql error data in the body.

Using graphiql or similar I get the graphql error presented, but with gql.client I only get

requests.exceptions.HTTPError: 400 Client Error: Bad Request for url: ...

due to

request.raise_for_status()

in https://github.com/graphql-python/gql/blob/master/gql/transport/requests.py#L39

These errors should be returned to the user, not just throw a 400-exception