CI: Failures due to pyarrow 0.11 in Travis 37 Locale Build 
Looks like recently the Travis 37 Locale Build has started picking up pyarrow 0.11.1

https://travis-ci.org/github/pandas-dev/pandas/jobs/719430999
pyarrow                   0.11.1           py37he6710b0_0 

This causes the pyarrow tests to run which seem to be failing.

Previously no pyarrow in env: https://travis-ci.org/github/pandas-dev/pandas/jobs/719138849 (passing build)

Feels like one of our deps has started to depend to pyarrow.