python-packages: Add package 'httpretty', v0.8.3.

This contains a context diff because the change is really very small and
gabrielfalcao/HTTPretty#180 cannot be used because it bumps the version
number.

The reason I'm not using sed here is because I deliberately want the
postPatch phase to fail for the next upstream version, so the patch/fix
is dropped on our side ASAP.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>