Get introspective schema on client side

Hello Team,

Im trying to get introspective schema on my android client. for that Im using following command.
`apollo-codegen download-schema http://swapi.graphene-python.org/--output schema.json`

But it returns me following error:
`error: Error while fetching introspection query result: invalid json response body at http://swapi.graphene-python.org/ reason: Unexpected token < in JSON at position 1`

I require schema.json at client side to query the server.

Kindly guide.
Thank you.