Enforce examples code-style

[penguinolog]

Checklist

• I've ensured that similar functionality has not already been implemented
• I've ensured that similar functionality has not earlier been proposed and declined
• I've branched off the master or python-dual-support branch
• I've merged fresh upstream into my branch recently
• I've ran tox successfully in local environment
• I've included docstrings and/or documentation and/or examples for my code (if this is a new feature)

[coveralls]

coverage: 73.566%. remained the same when pulling fc90aed on penguinolog:examples_code_style into b70be02 on urwid:master.