CLN: resource warnings

[jreback]

https://travis-ci.org/pydata/pandas/jobs/150623749

so we have warnings enabled on the 3.5/dev build. Lots of resource warnings....

[jreback]

@gfyoung an odd one here.

................................./home/travis/build/pydata/pandas/pandas/io/parsers.py:1904: FutureWarning: split() requires a non-empty pattern match.
  yield pat.split(line.strip())

[gfyoung]

That's due to a regex matching the empty string somewhere in one of the tests. Can try to patch that.

As for the other ResourceWarnings, I think it's because files are being closed before being destroyed, but in this instance, not sure why that would be happening given our test construction.

[jreback]

these only happen in PY3 fyi. Maybe its more strict.

[gfyoung]

Yes, it's because that warning was introduced in Python 3. Again, not 100% sure why they are occurring, since that implies that the file object is getting deleted before it is closed, and we're using with statements everywhere in the tests.