Fix up some docstrings.

The version.py docstrings were a) not PEP compliant and b) somewhat
out of sync with the code.

Change-Id: I87c4134ef80fd9e6fd57b66c58c3c5920ee0b6b6
Return the real class in VersionInfo __repr__.

Change-Id: I52337fd704a0d4b38f9562d88dcdf5952cf7b422
Factor run_cmd out of the base class.

I want to reuse this for factoring out some fixtures, so make it
reusable.

Change-Id: I7035a514adf889a8ebaadff9ae873341804fe099
Fixes blocking issue on Windows

On Windows, environment variables can not be unicode.

Change-Id: I8c7fd7627d7f733e0db8690a39e7128b7fe2ebcf
Closes-bug: #1294246
Make tools/integration.sh take a branch

Instead of always using master branch support the option to use stable
branches. Read the branch via the $OVERRIDE_ZUUL_BRANCH environmental
variable that devstack-gate sets

Change-Id: Iab4ae1efddc4dca38dcd3779dae1a79ddc2b0852
Merge "Make tools/integration.sh take a branch"
Merge "Fixes blocking issue on Windows"