Hack to fix "ImportError: No module named pwd" in AppEngine.

Import stack (on Ubuntu 13.10, Python 2.7.4):
  File "/home/tom/khan/webapp/third_party/requests/utils.py", line 19, in <module>
    from netrc import netrc, NetrcParseError
  File "/usr/lib/python2.7/netrc.py", line 5, in <module>
    import os, stat, shlex, pwd