Revert "travis: sudo is no longer required for python3.7 env"
Revert "travis: sudo is no longer required for python3.7 env"

This reverts commit 6c1537dafd89ba7d1b3fd5227d413fe45e322516.

Does not quite work yet without sudo. not sure why.
Let's keep it in.
https://twitter.com/cosimolupo/status/1052139428418899968

fonttools/fonttools,googlefonts/fonttools