[bug 1075563] Fix missing flake8 issue
[bug 1075563] Fix missing flake8 issue

In the conventions chapter, we suggest that the developer use the
pre-commit hook we have to lint code before it gets committed. However,
we needed to tell the developer to install flake8 first.

This fixes that.

lgp171188/fjord,DESHRAJ/fjord,DESHRAJ/fjord,rlr/fjord,hoosteeno/fjord,staranjeet/fjord,hoosteeno/fjord,rlr/fjord,lgp171188/fjord,rlr/fjord,lgp171188/fjord,mozilla/fjord,rlr/fjord,Ritsyy/fjord,staranjeet/fjord,hoosteeno/fjord,mozilla/fjord,DESHRAJ/fjord,hoosteeno/fjord,lgp171188/fjord,staranjeet/fjord,Ritsyy/fjord,mozilla/fjord,staranjeet/fjord,Ritsyy/fjord,mozilla/fjord,Ritsyy/fjord