TST: test_mixed_freq_regular_first failing on master
Started with https://travis-ci.org/pandas-dev/pandas/builds/232766866, which clearly (I think?) isn't to blame.

I don't see any differences in dependencies between https://travis-ci.org/pandas-dev/pandas/jobs/232654666 and https://travis-ci.org/pandas-dev/pandas/jobs/232766873 will dig in more later.