Create the output_dir for the test subcommand.

This change creates the output directory for the test subcommand if it
does not yet exist. If it exists, use it. Any other exceptions are
re-raised.

Change-Id: I487c69e70f9b6c475691ca4fef4669a0c318ab55
Add hacking to requirements

Solely for the transitive dependencies.  Ignore errors from hacking
as do the other openstack-infra python projects.

Change-Id: Ib5953c31a5380f9f57c7f79e1ce0699aef5eb629
Merge "Add hacking to requirements"