Merge pull request #225 from asherf/black

Run lint under python 3.8

Author: asherf

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = {py35,py36,py37,py38}-django{210,220}-{end2end,unittests},py37-lint
+envlist = {py35,py36,py37,py38}-django{210,220}-{end2end,unittests},py38-lint
 
 [testenv]
 deps =
@@ -19,7 +19,7 @@ commands =
     unittests: coverage run --source=django_prometheus setup.py test
     unittests: python setup.py sdist bdist_wheel
 
-[testenv:py37-lint]
+[testenv:py38-lint]
 deps =
     black
     flake8