Merge branch 'unbreak-builds' into 'master'

Force flake8 test to below 3.x

The current version (0.8) of `flake8-import-order` still uses `parser.config_options` and so all builds fail because it installs Flake8 3.x.

Now the repository of that plugin already accounted for that but as long as it isn't released it'll cause all new builds to fail. Alternatively I can repurpose this merge request to actually enforce a newer version of `flake8-import-order` which supports Flake8 3.x.

See merge request !84