Unable to upgrade pip

Try install it with easy_install:

easy_install -U pip

I had the same issue for a long time and figured out the solution today. When you install pip via python-pip, you download from the deprecated Linux server. You should download from the python server. To solve this, do the following:

sudo apt-get purge pip
sudo apt-get install python-setuptools
sudo apt-get install python-dev 
sudo easy_install pip 
pip install pip --upgrade 

This is caused by a conflict between a version of pip provided by a system package, like python-pip, and a version provided by PyPI through pip itself.

To fix this, simply remove python-pip with sudo apt-get purge python-pip.

If you had already used the old version of pip to install a newer version, this should leave the updated version in /usr/local/bin. If not, you can install the most recent version of Pip from scratch with:

Pip for Python 2.7:

curl --silent --show-error --retry 5 https://bootstrap.pypa.io/get-pip.py | sudo python2.7

Pip for Python 3.x:

curl --silent --show-error --retry 5 https://bootstrap.pypa.io/get-pip.py | sudo python3