Error while using bench update

bench update
Traceback (most recent call last):
File “/usr/local/bin/bench”, line 6, in
from pkg_resources import load_entry_point
File “/usr/local/lib/python2.7/dist-packages/pkg_resources/init.py”, line 3036, in
@_call_aside
File “/usr/local/lib/python2.7/dist-packages/pkg_resources/init.py”, line 3020, in _call_aside
f(*args, **kwargs)
File “/usr/local/lib/python2.7/dist-packages/pkg_resources/init.py”, line 3049, in _initialize_master_working_set
working_set = WorkingSet._build_master()
File “/usr/local/lib/python2.7/dist-packages/pkg_resources/init.py”, line 656, in _build_master
return cls._build_from_requirements(requires)
File “/usr/local/lib/python2.7/dist-packages/pkg_resources/init.py”, line 669, in _build_from_requirements
dists = ws.resolve(reqs, Environment())
File “/usr/local/lib/python2.7/dist-packages/pkg_resources/init.py”, line 854, in resolve
raise DistributionNotFound(req, requirers)
pkg_resources.DistributionNotFound: The ‘GitPython==0.3.2.rc1’ distribution was not found and is required by bench