Fix pristine editable install

[bonjourmauko]

Fixes #1136

Technical changes

• Fix pylint dependency in fresh editable installations
  • Ignore pytest requirement, used to collect test cases, if it is not yet installed.

[coveralls]

Coverage remained the same at 78.94% when pulling a2b4dd5 on fix-pristine-editable-install into 3eb157f on master.

[MattiSG]

Thank you for this contribution!
Could you please give an example to reproduce the error you encountered and intend to fix with this changeset? 🙂 I don't understand how it is possible to run make test-core without pytest installed, yet openfisca installed.

[MattiSG]

Sorry, I just saw the link to #1136 🤦 Trying to reproduce now 🙂

[MattiSG]

• I could reproduce the issue described in #1136.
• Maintaining make install on top of the installation procedure described in the README is consistent with #1040.
• I checked flake8 v4 changelog, and I believe the breaking changes are not impactful for reusers.

While I believe silencing errors has potential side effects (see #1138 (comment)) and is not optimal (I would prefer that we stop test-core from being called when make install is called!), I can approve the current changeset.

[bonjourmauko]

Thanks @MattiSG , I agree and actually find make increasingly painful to maintain as a tool. I hope we converge sooner than later to a more democratic and sustainable task manager for OpenFisca.