Try to work around installation failures on Travis CI
Try to work around installation failures on Travis CI

Refer to the following build for details:

  https://travis-ci.org/xolox/python-vcs-repo-mgr/builds/116062904

The 'python setup.py install' command uses setuptools (easy_install) to install
Mercurial and this seems to fail deep inside the setup.py script (sandboxed by
setuptools). To be honest I'm not all that interested in the gory details, I'm
just curious to see if pip and pip-accel can make it work (a first step towards
understanding and resolving the issue) ...

xolox/python-vcs-repo-mgr,xolox/python-vcs-repo-mgr