Bump pylint from 1.8.4 to 2.2.2

Bumps [pylint](https://github.com/PyCQA/pylint) from 1.8.4 to 2.2.2.
- [Release notes](https://github.com/PyCQA/pylint/releases)
- [Changelog](https://github.com/PyCQA/pylint/blob/master/ChangeLog)
- [Commits](pylint-dev/pylint@pylint-1.8.4...pylint-2.2.2)

Signed-off-by: dependabot[bot] <support@dependabot.com>

requirements-dev.txt

@@ -2,7 +2,7 @@
 django-autofixture==0.12.1
 django-debug-toolbar==1.9.1
 ipython
-pylint==1.8.4
+pylint==2.3.1
 pylint-django==0.11
 pytest==4.3.0
 pytest-cov==2.6.1