运行pip list，抛出异常，这是什么情况

执行pip list，抛出下面异常，不清楚是什么状况

 Exception:
    Traceback (most recent call last):
      File "/usr/lib/python2.7/dist-packages/pip/basecommand.py", line 122, in main
        status = self.run(options, args)
      File "/usr/lib/python2.7/dist-packages/pip/commands/list.py", line 80, in run
        self.run_listing(options)
      File "/usr/lib/python2.7/dist-packages/pip/commands/list.py", line 142, in run_listing
        self.output_package_listing(installed_packages)
      File "/usr/lib/python2.7/dist-packages/pip/commands/list.py", line 151, in output_package_listing
        if dist_is_editable(dist):
      File "/usr/lib/python2.7/dist-packages/pip/util.py", line 348, in dist_is_editable
        req = FrozenRequirement.from_dist(dist, [])
      File "/usr/lib/python2.7/dist-packages/pip/__init__.py", line 236, in from_dist
        assert len(specs) == 1 and specs[0][0] == '=='

AssertionError

把这个告警注释掉以后，又出了了新的问题

Exception:
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/pip/basecommand.py", line 122, in main
    status = self.run(options, args)
  File "/usr/lib/python2.7/dist-packages/pip/commands/list.py", line 80, in run
    self.run_listing(options)
  File "/usr/lib/python2.7/dist-packages/pip/commands/list.py", line 142, in run_listing
    self.output_package_listing(installed_packages)
  File "/usr/lib/python2.7/dist-packages/pip/commands/list.py", line 151, in output_package_listing
    if dist_is_editable(dist):
  File "/usr/lib/python2.7/dist-packages/pip/util.py", line 348, in dist_is_editable
    req = FrozenRequirement.from_dist(dist, [])
  File "/usr/lib/python2.7/dist-packages/pip/__init__.py", line 237, in from_dist
    version = specs[0][1]
IndexError: list index out of range

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我把pip升级后，问题解决。
本地执行了一把 pip install --upgrade pip

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标准解决方案请到Stackoverflow查阅