selector2: vendor selector2 library This library was a backport of the Python 3 "selectors" library. It is useful to provide a better selector interface for Python2, to address some issues of the plain old select.select, mentioned in the next patch. The code [1] was ported using the MIT license, with some minor modifications to make our test happy: 1. "# no-check-code" was added since it's foreign code. 2. "from __future__ import absolute_import" was added. 3. "from collections import namedtuple, Mapping" changed to avoid direct symbol import. [1]: https://github.com/SethMichaelLarson/selectors2/blob/d27dbd2fdc48331fb76ed431f44b6e6956de7f82/selectors2.py # no-check-commit