Fix failing master test

[spockNinja]

Problem

Master tests started failing in a strange way.

See https://travis-ci.org/graphql-python/graphene-django/jobs/285520455

It is only failing for the Django 1.8 build. It took a while to pinpoint why, as nothing in our repository changed related to the failure.

encode/django-rest-framework@c674687

Is what started the failure. DRF 3.7.0 does not support Django 1.8 anymore.

Solution

For now, I have a conditional pip install override for our 1.8 build. A few other options exist as well.

• We could follow suit and stop supporting 1.8.
• We could pin the general requirement in setup.py to be <3.7.0.
• Maybe something else?

[coveralls]

Coverage increased (+0.2%) to 92.999% when pulling 768fca6 on spockNinja:fix_master_failing_test into 77f0361 on graphql-python:master.

[spockNinja]

@syrusakbary

I think I've taken the most reasonable and open approach to this strange test failure. It isn't pretty, but it allows us to maintain 1.8 support and also continue to test against the latest drf.

[syrusakbary]

Looks good @spockNinja!
Merging :)