`Twython.callback_url` does not exist

[jvanasco]

This error popped up while working on a project that subclasses this.

There is a backup function to invoke self.callback_url on the Twython class, however that attribute is never assigned or defined.

Looking at the history of the project, I think this was marked for deprecation in 2011 and removed in 2013, but this reference somehow remained.

https://github.com/ryanmcgrath/twython/blob/0c405604285364457f3c309969f11ba68163bd05/twython/api.py#L359-L361

[ryanmcgrath]

Wow! Talk about ancient history. How were you triggering this - just a standard OAuth flow?

[jvanasco]

I have a project that integrates oauthlib into the Pyramid framework. I based the client class for the tests on Twython.

I was updating it with typing support, and one of the linters picked this up. I think mypy. I traced it back to Twython, then audited your code and the repo's history -- and found the tickets where a bunch of this stuff was reorganized.