为什么我在Mac上运行pip冻结时会得到AssertionError？

Question

我已经尝试了this SO问题中提供的解决方案。

我仍然得到以下内容：

~ $pip freeze
Exception:
Traceback (most recent call last):
  File "/Library/Python/2.7/site-packages/pip-1.4.1-py2.7.egg/pip/basecommand.py", line 134, in main
status = self.run(options, args)
  File "/Library/Python/2.7/site-packages/pip-1.4.1-py2.7.egg/pip/commands/freeze.py", line 73, in run
req = pip.FrozenRequirement.from_dist(dist, dependency_links, find_tags=find_tags)
  File "/Library/Python/2.7/site-packages/pip-1.4.1-py2.7.egg/pip/__init__.py", line 194, in from_dist
assert len(specs) == 1 and specs[0][0] == '=='
AssertionError

Storing complete log in filepath/Library/Logs/pip.log