Common py.test support for Diffeo tests.
If this package is installed, then you can run py.test with additional
command-line arguments --runperf, --runslow, -runload, or -run-integration.
Tests marked with @pytest.mark.performance, @pytest.mark.slow,
@pytest.mark.load, and pytest.mark.integration respectively, will not
be run unless the corresponding command-line option is present.
This package also provides a redis_address fixture to get the
location of an external Redis installation. This must be provided via
a --redis-address command-line argument.