Incorporating your patch into upstream...

[al-the-x]

@alexhughson Just ran into the same problem connecting to Pearson that you did. I Were you using the OAuth 1.0a endpoint, too? We're using the requests + requests-oauthlib modules to make requests, but I don't see how oauthlib permits additional signature methods to be used for OAuth 1.0a; did you run into a similar problem?

[al-the-x]

FWIW, I ended up patching requests-oauthlib and oauthlib to allow registering custom signature methods (see oauthlib/oauthlib#239).