Heroku pip problem

Tive um problema ao implantar um aplicativo muito simples no Heroku. Aqui está o erro:

-----> Installing dependencies using Pip (1.3.1)
           Exception:
           Traceback (most recent call last):
             File "/app/.heroku/python/lib/python2.7/site-packages/pip-1.3.1-py2.7.egg/pip/basecommand.py", line 139, in mai
    n
               status = self.run(options, args)
             File "/app/.heroku/python/lib/python2.7/site-packages/pip-1.3.1-py2.7.egg/pip/commands/install.py", line 240, i
    n run
               for req in parse_requirements(filename, finder=finder, options=options):
             File "/app/.heroku/python/lib/python2.7/site-packages/pip-1.3.1-py2.7.egg/pip/req.py", line 1356, in parse_requ
    irements
               req = InstallRequirement.from_line(line, comes_from)
             File "/app/.heroku/python/lib/python2.7/site-packages/pip-1.3.1-py2.7.egg/pip/req.py", line 96, in from_line
               elif os.path.isdir(path) and (os.path.sep in name or name.startswith('.')):
             File "/app/.heroku/python/lib/python2.7/genericpath.py", line 41, in isdir
               st = os.stat(s)
           TypeError: must be encoded string without NULL bytes, not str

           Storing complete log in /app/.pip/pip.log

     !     Push rejected, failed to compile Python app

Uma vez que não há acesso aos arquivos no Heroku (eles são substituídos). Disparei pip na minha máquina local para ver o log:

C:Python27Scriptspip-script.py run on 10/12/13 02:48:15
Exception:
Traceback (most recent call last):
  File "C:Python27libsite-packagespip-1.3.1-py2.7.eggpipbasecommand.py", line 139, in main
    status = self.run(options, args)
  File "C:Python27libsite-packagespip-1.3.1-py2.7.eggpipcommandsinstall.py", line 240, in run
    for req in parse_requirements(filename, finder=finder, options=options):
  File "C:Python27libsite-packagespip-1.3.1-py2.7.eggpipreq.py", line 1356, in parse_requirements
    req = InstallRequirement.from_line(line, comes_from)
  File "C:Python27libsite-packagespip-1.3.1-py2.7.eggpipreq.py", line 118, in from_line
    return cls(req, comes_from, url=url)
  File "C:Python27libsite-packagespip-1.3.1-py2.7.eggpipreq.py", line 43, in __init__
    req = pkg_resources.Requirement.parse(req)
  File "C:Python27libsite-packagespkg_resources.py", line 2510, in parse
    reqs = list(parse_requirements(s))
  File "C:Python27libsite-packagespkg_resources.py", line 2424, in parse_requirements
    raise ValueError("Missing distribution spec", line)
ValueError: ('Missing distribution spec', 'xffxfeFx00lx00ax00sx00kx00=x00=x000x00.x001x000x00.x001x00')

parece que meu arquivo requirements.txt foi codificado como UTF e pip não gostou disso. A conversão para ASCII resolve o problema.