Not handling could not find a version that satisfies the requirement

[mkouhei]

[2015-05-29 13:04:20,492: CRITICAL/Worker-1] Could not find a version that satisfies the requirement swift>=1.9.1 (from swiftkerbauth) (from versions: 1.0.2.linux-x86_64, 1.0.2)
[2015-05-29 13:04:20,492: WARNING/Worker-1] Some externally hosted files were ignored as access to them may be unrelia
ble (use --allow-external swift to allow).
[2015-05-29 13:04:20,508: ERROR/MainProcess] Task pygraph.tasks.gen_dependency[f01f30ad-d080-4c16-9c7e-f4306f1a2656] raised unexpected: DistributionNotFound('No matching distribution found for swift>=1.9.1 (from swiftkerbauth)',)
Traceback (most recent call last):
(snip)
  File "/path/to/venv/lib/python3.4/site-packages/py_deps-0.4.1-py3.4.egg/py_deps/deps.py", line 118, in __init__
  File "/path/to/venv/lib/python3.4/site-packages/py_deps-0.4.1-py3.4.egg/py_deps/deps.py", line 181, in trace_chain
  File "/path/to/venv/lib/python3.4/site-packages/py_deps-0.4.1-py3.4.egg/py_deps/deps.py", line 169, in _list_requires
  File "/path/to/venv/lib/python3.4/site-packages/py_deps-0.4.1-py3.4.egg/py_deps/deps.py", line 160, in _download
  File "/path/to/venv/lib/python3.4/site-packages/pip/req/req_set.py", line 317, in prepare_files
    functools.partial(self._prepare_file, finder))
  File "/path/to/venv/lib/python3.4/site-packages/pip/req/req_set.py", line 304, in _walk_req_to_install
    more_reqs = handler(req_to_install)
  File "/path/to/venv/lib/python3.4/site-packages/pip/req/req_set.py", line 439, in _prepare_file
    req_to_install.populate_link(finder, self.upgrade)
  File "/path/to/venv/lib/python3.4/site-packages/pip/req/req_install.py", line 244, in populate_link
    self.link = finder.find_requirement(self, upgrade)
  File "/path/to/venv/lib/python3.4/site-packages/pip/index.py", line 563, in find_requirement
    'No matching distribution found for %s' % req
pip.exceptions.DistributionNotFound: No matching distribution found for swift>=1.9.1 (from swiftkerbauth)