Python 3.4 reached end-of-life in March 2019 [0].

Clean up remaining configuration, corner-case and documentation references
to this prior Python version.

[0] https://www.python.org/dev/peps/pep-0429/#release-schedule

Fixes: 155b93e1 ("travis: Drop python3.4")
Signed-off-by: Rhys Kidd <rhyskidd@gmail.com>
Reviewed-by: Eric Engestrom <eric@engestrom.ch>