use install_requires in setup.py

[Mat Lehmann]

easy_install and it's successors (buildout and I believe also pip) use the 'install_requires' parameter to setup instead of the 'requires' parameter.

Since python-fixtures only uses 'requires', 'testtools' is not installed as a dependency and running tests that use fixtures fails with an ImportError.

[Robert Collins (lifeless)]

Fixed by using pbr.

[Lennart Regebro (lregebro)]

Unfortunately the mock;python_version<'3.3' syntax in test-requirements.txt now breaks pip installs.

[Robert Collins (lifeless)]

Yes, it will do that if your pbr is < 1.2. or your pip is < 6.0. Unfortunately setuptools doesn't handle versioned setup_requires dependencies at all well, which is why I don't have one here.