message: Render raw response on error fetching schema.
  Closes
diff: @@ -425,9 +425,11 @@ export class GraphiQL extends React.Component {
  });
  }
  }).catch(error => {
  + // Report both the error message, and the returned result.
  + const errorMessage = error && String(error.stack || error);
  this.setState({
  schema: null,
  - response: error && String(error.stack || error)
  + response: [errorMessage, result].filter(x => x).join('\n\n')
  });
  });
  }
  