[PATCH] setup.py: attempt to use setuptools

[Gregory Szorc]

# HG changeset patch
# User Gregory Szorc <gregory.szorc at gmail.com>
# Date 1421431223 28800
#      Fri Jan 16 10:00:23 2015 -0800
# Node ID 711fa69653f69a7059966fff1dae1a352244b781
# Parent  049a9e3a078d7c988cb12ed456aad6ec2779ea69
setup.py: attempt to use setuptools

The Python Packaging User Guide recommends setuptools over distutils
(https://packaging.python.org/en/latest/distributing.html).

setuptools.setup should be a drop-in replacement for
distutils.core.setup and this patch should "just work." That being said,
setuptools does differ from distutils. I wouldn't be surprised if this
change broke Mercurial packaging somewhere. If it does, it should be
easy enough to revert.

With this patch applied, I did notice a new warning when running
setup.py:

  UserWarning: The version specified requires normalization, consider
using '3.2.4+668.41fac217e2e4' instead of '3.2.4+668-41fac217e2e4'.

Furter research indicates that setuptools may break our current
dev versioning format in the future.

The impetus for this patch is to work around
https://bugs.python.org/issue23246, which was preventing me from easily
building Mercurial on Windows using the Visual C++ for Python
distribution.

In the future, this patch may open the door to other distribution
potentials for Mercurial, including wheels, which the Python world is
slowly moving to. On my machine, |python setup.py bdist_wheel| does
produce a wheel. But I haven't tested whether the wheel is sane.

diff --git a/setup.py b/setup.py
--- a/setup.py
+++ b/setup.py
@@ -66,10 +66,16 @@ else:
 import os, stat, subprocess, time
 import re
 import shutil
 import tempfile
+
+try:
+    from setuptools import setup
+except:
+    from distutils.core import setup
+
 from distutils import log
-from distutils.core import setup, Command, Extension
+from distutils.core import Command, Extension
 from distutils.dist import Distribution
 from distutils.command.build import build
 from distutils.command.build_ext import build_ext
 from distutils.command.build_py import build_py