[PATCH 1/6] Bumped version of requests python library to unbreak build

RB_ID=265741
TBR=true

(sapling split of 3bebb6e1182fd0c72c6d222d46f618cf8f8e8fdc)
[PATCH 4/6] fix jira resolve for REV project

RB_ID=267861

(sapling split of 3db31fc6d13bb8fa1b1324fe58053cf620766dfc)
[PATCH 5/6] make pex dependency resolution hermetic

tl;dr this greatly simplifies the PEX environment resolution code and fixes
a bunch of bugs

Main changes:
  1) splits PEXEnvironment out of pex.py and into environment.py
  2) removes the duplication of WorkingSet/Environment state (this was super
     confusing to me before, now it makes a bit more sense.)
  3) only considers dependencies that originate from the internal cache
     rather than internal + install cache [this fixes AWESOME-4425]
  4) explodes distributions into the zipfile so that the recursive zipimporter
     is no longer necessary.

RB_ID=265251

(sapling split of 002cf22ce8c96b804abc159f1942217265dea75c)
[PATCH 6/6] add interpreter selection support to python build/test

Plumbs through PythonInterpreter support to build/test.
Switches twitter.common.python tests to mock from mox.

RB_ID=267043

(sapling split of 4b0a99bc801818d16eb70af152966fb0b35ba60e)
Fixup tests broken by new EggLink behavior that rejects eggs without version and python version in the name.
Merge pull request #198 from jsirois/jsirois/sync/python-4

Sync python-commons changes over the last week