I found a post that describes this error with python requests.
The trick is you have to change the ‘Content-Type’ header to ‘application/json’.
Then I had to change the post string to:
r = requests.post(url,json={"query": query, "variables": params}, headers=headers)
https://github.com/Shopify/graphql-js-client/issues/132
This is how you post to GraphQL using Python request. This may be very helpful to other people.