kennethreitz/requests — pull request #1898 by Zopieux (2014-02-02 16:09:22+00:00)
Title: Made .history type consistent (tuples only)

An empty history was represented by an empty list whereas a non-empty history was a tuple.
Now the type of .history is always a tuple, so it does not break code such as `req.history + (req,)`.