1160794 - use newer python-requests

See commit 6db8a3efc in pulp repository for more detail as to why this is
needed.
Hmmm, do we really require this from an API perspective though? IME, package requirements are more about API requirements than bug fixes. This way it's up to the user to decide if they want the upgrade or not (i.e., they can decide based on whether the bug fix is important to them.)