Log Message:
py-daemon: updated to 2.3.1

Version 2.3.1
=============

Bugs Fixed:

* Avoid operations on a closed stream file when detecting a socket.
* Correct use of names to allow `from daemon import *`.

Changed:

* Speed daemon start time by computing candidate file descriptors once.
* Remove incorrect double-patch of objects in test cases.
* Deprecate helper function `is_socket`.

  The function incorrectly causes `ValueError` when the file object is already
  closed. Migrate to the new `is_socket_file` helper function instead.

Removed:

* Drop backward-compatible helpers that provided Python 2 support.

  * declaration of source encoding ‘utf-8’
  * absolute_import
  * unicode_literals
  * module-level metaclass `type`
  * unification of str with unicode type
  * renamed standard library exceptions and modules
  * raise exception from context exception

  All these are default behaviour in Python 3 and need no special
  handling.