MESSAGE: /usr/bin/pip: No such file or directory but then checked which pip was being called.

execute: which pip

after that:
/usr/local/bin/pip uninstall pip 
apt-get remove python-pip 
apt-get install python-pip 

HOW TO UPGRADE YOUR PYTHON VERSION

sudo add-apt-repository ppa:jonathonf/python-3.x
sudo apt update
sudo apt install python3.x

Afterchange the default Python folder by this way:

sudo rm /usr/bin/python
sudo ln -s /usr/bin/python3 /usr/bin/python
Check the default


for check your python version:
 python -V