'certificate' parameter in RemoteCallbacks doesn't work

[nu11ptr]

Looking at the code, I think the 'certificate' init param is supposed to be named 'certificate_check' so that if it is set, it overrides the class function (I believe this is how 'credentials' is working). As it stands, I don't see anywhere in the class where 'certficate' is referenced (fetch_opts it only references 'certificate_check') and some tests to self-signed servers didn't work until I created my own subclass with my own version of 'certificate_check'.