TST: failure on s3 mocking
master seems to fail recently: https://travis-ci.org/pandas-dev/pandas/jobs/367585545

on ``pandas/tests/iotest_parquet.py -k s3``.

works locally for me. very odd as this is mocked and shouldn't ever have a connection error.

In particular xfailing:  https://github.com/pandas-dev/pandas/commit/336fba7c0191444c3328009e6d4f9f5d00ee224b
- [ ] ``test_read_csv_chunked_download`` in ``pandas.tests.io.test_network.py``
- [ ] ``test_s3_roundtrip`` for fp & pyarrow in ``pandas.testsio.test_parquet.py``
