Fix bug where a module import set up logging, pin doctools for Py2

[piskvorky]

• Module imports must never issue logging events, because logging is not set up in the main app yet. The logging event triggered a default (unwanted) config init.
• warnings.warn better, but in this case, we can more simply re-use the existing functionality from gensim.utils

The bug manifested itself as an unexpected log output on Gensim import:

 2019-07-04 23:22:48,902 [MainProcess/98263] [INFO] gensim.summarization.textcleaner:37: 'pattern' package not found; tag filters are not available for English

This may be a deeper issue with the summarization subpackage doing weird stuff. This PR is only a surface stop-gap, I didn't look any deeper.

[mpenkov]

Looks like the tests are failing. Did you forget to check some changes in? Or is this a work in progress?

[piskvorky]

I didn't run it, just edited the faulty file on Github, to get rid of the logging setup. Good we have the tests!

Edited some more now, hopefully that fixes it.

[mpenkov]

Tests are still failing, but the cause seems to be some Py2 bs with one of our dependencies.

[piskvorky]

According to pywbem/pywbem#1788, pinning docutils to 0.14 helps… not sure where to do that though. Is docutils some internal dependency of Sphinx?

[mpenkov]

Finally got around to looking at this. Pinned doctools in setup.py, let's see if it helps.