mypy: fix mysterious build error

hauntsaninja · hauntsaninja · commit 66ebb223a9c9 · 2020-02-10T16:17:12.000-08:00
diff --git a/.travis.yml b/.travis.yml
@@ -82,6 +82,7 @@ jobs:
 install:
 - pip install -U pip setuptools
 - pip install -U tox==3.9.0
+- pip install -U six>=1.12
 - tox --notest
 
 # This is a big hack and only works because the layout of our directories
