The support for Python 2.7 is deprecated on newer versions of pip, hence the reason why you're noticing this error here.
In order for you to maintain the sanity with Python 2.7 and pip, either maintain yourself to lower version of pip using the pip installer itself
pip install --upgrade pip==20.3
or make use of the Python 2.7 specific version of get-pip.py
curl https://bootstrap.pypa.io/2.7/get-pip.py --output get-pip.py
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