当我尝试命令pip install service_identity时，它返回以下错误。
Downloading/unpacking service-identity
Downloading service_identity-14.0.0-py2.py3-none-any.whl
Cleaning up...
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/install.py", line 278, in run
requirement_set.prepare_files(finder, force_root_egg_info=self.bundle, bundle=self.bundle)
File "/usr/lib/python2.7/dist-packages/pip/req.py", line 1259, in prepare_files
)[0]
IndexError: list index out of range
我也尝试过sudo，但返回了同样的错误。怎么解决这个问题？