Yes, fix verified.

$ bin/python -c "import setuptools; print setuptools.__version__"
0.6c12
$ bin/easy_install TracAddHeadersPlugin
Searching for TracAddHeadersPlugin
Reading http://pypi.python.org/simple/TracAddHeadersPlugin/
Reading http://www.trac-hacks.org/wiki/AddHeadersPlugin
No local packages or download links found for TracAddHeadersPlugin
error: Could not find suitable distribution for Requirement.parse
('TracAddHeadersPlugin')

Fixed in trunk and branch; please verify w/ "easy_install setuptools==dev06".

The bug seems to have introduced by r75383

This was using setuptools-0.6c11 on Python 2.6.4 / MacOSX 10.6.

> easy_install TracAddHeadersPlugin
Searching for TracAddHeadersPlugin
Reading http://pypi.python.org/simple/TracAddHeadersPlugin/
Reading http://www.trac-hacks.org/wiki/AddHeadersPlugin
No local packages or download links found for TracAddHeadersPlugin
Best match: None
Traceback (most recent call last):
  File "/Users/sridharr/.local/bin/easy_install", line 8, in <module>
    load_entry_point('setuptools==0.6c11', 'console_scripts', 'easy_install')()
  File "/Users/sridharr/.local/lib/python2.6/site-
packages/setuptools/command/easy_install.py", line 1712, in main
    with_ei_usage(lambda:
  File "/Users/sridharr/.local/lib/python2.6/site-
packages/setuptools/command/easy_install.py", line 1700, in with_ei_usage  
    return f()
  File "/Users/sridharr/.local/lib/python2.6/site-
packages/setuptools/command/easy_install.py", line 1716, in <lambda>
    distclass=DistributionWithoutHelpCommands, **kw
  File 
"/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/distutils/core.
py", line 152, in setup
    dist.run_commands()
  File 
"/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/distutils/dist.
py", line 975, in run_commands
    self.run_command(cmd)
  File 
"/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/distutils/dist.
py", line 995, in run_command
    cmd_obj.run()
  File "/Users/sridharr/.local/lib/python2.6/site-
packages/setuptools/command/easy_install.py", line 211, in run
    self.easy_install(spec, not self.no_deps)
  File "/Users/sridharr/.local/lib/python2.6/site-
packages/setuptools/command/easy_install.py", line 434, in easy_install
    self.local_index
  File "/Users/sridharr/.local/lib/python2.6/site-
packages/setuptools/package_index.py", line 475, in fetch_distribution
    return dist.clone(location=self.download(dist.location, tmpdir))
AttributeError: 'NoneType' object has no attribute 'clone'