ERR: fix exception propogation for datetime parsing functions, noted in python 3.6
 closes #14561
so after this PR: https://travis-ci.org/jreback/pandas/jobs/176738690

get a small number of failures (and bunch of deprecation warnings). but looks like this fixes the xref issue.
 @jreback Thanks!

Just a question, what is the reason for the change in setup.py?
 changes to that file (.pxd) were not in the build chain - it's a dependency so should have been
