Log Message:
Update py-gflags to 3.1.2, add Python 3 support.

Also part of PR pkg/52941.

Fri Oct 27 00:00:01 2017  Google Inc. <google-gflags@googlegroups.com>
* python-gflags: version 3.1.2.
* New API names for compatibility with abseil-py.

Mon Jan 30 00:00:01 2017  Google Inc. <google-gflags@googlegroups.com>
  * python-gflags: version 3.1.1.
  * Added PEP8 style method/function aliases.

Tue Nov 01 00:00:01 2016  Google Inc. <google-gflags@googlegroups.com>
  * python-gflags: version 3.1.0.
  * Python3 compatibility
  * Removed UnrecognizedFlag exception.
  * Replaced flags.DuplicateFlag with flags.DuplicateFlagError.
  * Moved the validators.Error class to exceptions.ValidationError.
  * Renamed IllegalFlagValue to IllegalFlagValueError.
  * Removed MutualExclusionValidator class, in favor of \ 
flags.MarkFlagsAsMutualExclusive.
  * Removed FlagValues.AddValidator method.
  * Removed _helpers.GetMainModule.
  * Use xml.dom.minidom to create XML strings, instead of manual crafting.
  * Declared PEP8-style names.
  * Added examples.

  * python-gflags: version 3.0.7.
  * Removed the unused method ShortestUniquePrefixes.
  * Removed _GetCallingModule function alias.

Fri Aug 05 00:00:01 2016  Google Inc. <google-gflags@googlegroups.com>

  * python-gflags: version 3.0.6
  * Declared pypi package classifiers.
  * Added support for CLIF flag processing (not included in python-gflags repo
    yet).

Thu May 12 00:00:01 2016  Google Inc. <google-gflags@googlegroups.com>

  * python-gflags: version 3.0.5
  * Added a warning when FLAGS.SetDefault is used after flags were parsed.
  * Added new function: MarkFlagsAsRequired.

Fri Apr 15 00:00:01 2016  Google Inc. <google-gflags@googlegroups.com>

  * python-gflags: version 3.0.4
  * One more fix for setup.py - this time about third_party package.

Mon Apr 11 00:00:01 2016  Google Inc. <google-gflags@googlegroups.com>

  * python-gflags: version 3.0.3
  * Fixed setup.py.
  * --noflag if argument is given is no longer allowed.
  * Python3 compatibility: removed need for cgi import.
  * Disallowed unparsed flag usage after FLAGS.Reset()

Thu Feb 09 11:55:00 2016  Google Inc. <google-gflags@googlegroups.com>

  * python-gflags: version 3.0.2
  * Fix MANIFEST.in to include all relevant files.

Thu Feb 04 22:23:00 2016  Google Inc. <google-gflags@googlegroups.com>

  * python-gflags: version 3.0.1
  * Some changes for python3 compatibility.
  * Automatically generate ordering operations for Flag.
  * Add optional comma compatibility to whitespace-separated list flags.

Tue Jan 12 16:39:00 2016  Google Inc. <google-gflags@googlegroups.com>

  * python-gflags: version 3.0.0.
  * A lot of potentially backwards incompatible changes since 2.0.
  * This version is NOT recommended to use in production. Some of the files and
    documentation has been lost during export; this will be fixed in next
    versions.