Pin pytest-django to <3.2.0 while we're still not on Django 1.11
Pin pytest-django to <3.2.0 while we're still not on Django 1.11

* pytest-django 3.2.0 dropped Django 1.8 support

Refs https://github.com/mozilla/addons-server/pull/8045

kumar303/addons-server,bqbn/addons-server,wagnerand/addons-server,wagnerand/olympia,eviljeff/olympia,mozilla/olympia,bqbn/addons-server,diox/olympia,psiinon/addons-server,kumar303/addons-server,wagnerand/addons-server,wagnerand/olympia,kumar303/olympia,mozilla/olympia,atiqueahmedziad/addons-server,mozilla/addons-server,aviarypl/mozilla-l10n-addons-server,psiinon/addons-server,diox/olympia,harry-7/addons-server,wagnerand/olympia,lavish205/olympia,wagnerand/addons-server,eviljeff/olympia,kumar303/olympia,mozilla/addons-server,mozilla/olympia,harry-7/addons-server,kumar303/olympia,harry-7/addons-server,diox/olympia,wagnerand/olympia,mozilla/olympia,bqbn/addons-server,diox/olympia,eviljeff/olympia,lavish205/olympia,atiqueahmedziad/addons-server,lavish205/olympia,atiqueahmedziad/addons-server,psiinon/addons-server,eviljeff/olympia,aviarypl/mozilla-l10n-addons-server,bqbn/addons-server,mozilla/addons-server,kumar303/addons-server,lavish205/olympia,wagnerand/addons-server,aviarypl/mozilla-l10n-addons-server,atiqueahmedziad/addons-server,mozilla/addons-server,psiinon/addons-server,aviarypl/mozilla-l10n-addons-server,harry-7/addons-server,kumar303/addons-server,kumar303/olympia