Revert "Remove optional setuptools import."

This reverts commit 50b28c5d7a.

Turns out we do need setuptools in at least one situation:
distutils chokes if there are broken symlinks anywhere in the source
tree, but in testing with a VM there may be "broken" symlinks that point
outside the directory shared with the VM.

setup.py

@@ -16,6 +16,12 @@
 
 import distutils.core
 import sys
+# Importing setuptools adds some features like "setup.py develop", but
+# it's optional so swallow the error if it's not there.
+try:
+    import setuptools
+except ImportError:
+    pass
 
 kwargs = {}
 

website/sphinx/releases/next.rst

@@ -4,7 +4,6 @@ What's new in the next version of Tornado
 In progress
 -----------
 
-* ``setup.py`` no longer imports setuptools on Python 2.x.
 * Colored logging configuration in `tornado.options` is compatible with
   the upcoming release of Python 3.3.
 * `tornado.simple_httpclient` is better about closing its sockets