pip freeze - unknown revision or path not in the working tre

While trying to get the list of the current package using pip freeze, it throws following error -

> pip freeze

Complete output from command /usr/bin/git rev-parse (detachedfrom0af02a9):

fatal: ambiguous argument '(detachedfrom0af02a9)': unknown revision or path not in the working tree.

Use '--' to separate paths from revisions, like this:

'git [...] -- [...]'

(detachedfrom0af02a9)

----------------------------------------

Command /usr/bin/git rev-parse (detachedfrom0af02a9) failed with error code 128

Storing complete log in /home/youraccount/.pip/pip.log

It's issue with the outdated pip package. To fix the issue -

You can upgrade it with following command -

pip install --upgrade pip

It should fix the issue.