Enable us to do `python -m jenkins_jobs ...`
which avoids the need to install executable in
user path.
Tests cli execution on each supported python version.
Uses default encoding workaround only on
python2, where is needed.
Change-Id: I4cd79fd51a8309d532e0e76723ecfbbda3e1ca6f
Signed-off-by: Sorin Sbarnea <ssbarnea@redhat.com>