Add flake8 check to Travis-CI matrix

[refeed]

Closes #263

[refeed]

A demo build can be seen here: https://travis-ci.org/refeed/kiwix-build/builds/510962532

[kelson42]

@refeed thx, but it looks like the CI fails.

[refeed]

0.01s$ [ -n "$encrypted_eba2f7543984_iv" ] && openssl aes-256-cbc -K $encrypted_eba2f7543984_key -iv $encrypted_eba2f7543984_iv -in travis/travisci_builder_id_key.enc -out travis/travisci_builder_id_key -d
The command "[ -n "$encrypted_eba2f7543984_iv" ] && openssl aes-256-cbc -K $encrypted_eba2f7543984_key -iv $encrypted_eba2f7543984_iv -in travis/travisci_builder_id_key.enc -out travis/travisci_builder_id_key -d" failed and exited with 1 during .

Hmm, yeah, you're right. But I think the cause of the failure isn't related to this PR. I'm gonna amend the commit to see if the CI could be green

[kelson42]

@mgauthier Any feedback about that PR?

[stale]

This pull request has been automatically marked as stale because it has not had recent activity. It will be now be reviewed manually. Thank you for your contributions.