The new "all" optional dependency target is intended to replicate the

old behavior of installing all python dependencies.
Documentation has been updated to reflect this.

Since this is just a change for pip dependencies I've done:

- pip install -e ./bot reviewbot-worker

- pip install -e ./bot reviewbot-worker[all]

To test if it installs and doesn't install flake8 under the default 

package and the all target, and according to the logs this is the case.