[Distutils] easy_install self upgrade/version check bug

[jason]

I've run into a problem where easy_install/setuptools continues to
recommend upgrading itself even after the upgrade has been installed. Steps
to reproduce on CentOS 5.2:

include ~/python in PYTHONPATH
include ~/bin in PATH

create ~/.pydistutils.cfg 
[install]
install_lib = ~/python
install_scripts = ~/bin

$ easy_install flup
...
Running flup-1.0.3.dev-20090608/setup.py -q bdist_egg --dist-dir
/tmp/easy_install-rPyZ6a/flup-1.0.3.dev-20090608/egg-dist-tmp-pm0o4x
The required version of setuptools (>=0.6c9) is not available, and
can't be installed while this script is running. Please install
 a more recent version first, using 'easy_install -U setuptools'.

(Currently using setuptools 0.6c5 (/usr/lib/python2.4/site-packages))
error: Setup script exited with 2
$ easy_install -U setuptools
...
Processing dependencies for setuptools
$ which easy_install
~/bin/easy_install
$ python -c 'import setuptools; print setuptools.__version__'
0.6c9
$ easy_install flup
...
Running flup-1.0.3.dev-20090608/setup.py -q bdist_egg --dist-dir
/tmp/easy_install-WoxTch/flup-1.0.3.dev-20090608/egg-dist-tmp-oFotRt
The required version of setuptools (>=0.6c9) is not available, and
can't be installed while this script is running. Please install
 a more recent version first, using 'easy_install -U setuptools'.

(Currently using setuptools 0.6c5 (/usr/lib/python2.4/site-packages))
error: Setup script exited with 2


At this point I thought it might be a problem with flup's setup.py or
ez_setup.py, but manually running python setup.py bdist_egg outside of
easy_install works fine.