Fix travis-ci build on django-netjsongraph (flake8 error)

OpenWISP

Currently the build for django-netjsongraph, one of the base modules used by OpenWISP 2, is broken.

Check the failed travis build and understand why, then perform a development installation (see the README), run the same check that fails on travis, ensure it fails, fix the error, commit following our guidelines on commit message style and open a pull request.

Don't forget to communicate with your mentors.

Task tags

python
travis
git
django
flake8

Students who completed this task

Alan Zhu

Task type

Code
Quality Assurance