debian/Jenkinsfile: Add file. Initiate CI builds.

See merge request !1

Python-2-variants don't have the concept of __pycache__ directories at
all, so using %pycache_only there is redundant.

Python-3-variants sprinkle __pycache__ directories wherever there are
.py files, which means that they are conveniently contained in the
"pyhoca" subdirectory of sitelib.

Older *SuSE versions, including Leap, just ignored files or directories
in the %files list that do not exist, but Tumbleweed is throwing an
error if you try to include a file or directory that does not exist.

The fix is easy: don't try to include the non-existent __pycache__
top-level directory.

This reverts commit 8ce1d32e.

This issue is temporarily reverted because it breaks ssh-agent based authentication.

This reverts commit 9eea3710.

{pyhoca-cli,pyhoca/cli/frontend.py}: Add --non-interactive cmdline option for forcefully preventing password queries on the TTY.

pyhoca-cli: Follow-up fix for --dpi switch. Fix input value verification. Only demand an integer, if args.dpi is set to something else than None.

pyhoca/cli/frontend.py: Fix reference before assignment error in resume_session() method. Thanks to Randy Goldenberg for spotting this. (Fixes: #1445).