Update tox from 2.9.1 to 3.20.1 (#20)

pyup-bot · web-flow · commit 75dfed3380ad · 2020-10-18T23:58:52.000-07:00
diff --git a/requirements_dev.txt b/requirements_dev.txt
@@ -3,7 +3,7 @@ bump2version==0.5.11
 wheel==0.35.1
 watchdog==0.10.3
 flake8==3.5.0
-tox==2.9.1
+tox==3.20.1
 coverage==4.5.1
 Sphinx==1.7.1
 twine==1.10.0
