title: how do I upgrade pip on Mac?
body: <p>I cannot upgrade pip on my Mac from the Terminal. </p>
  
  <p>According to the documentation I have to type the command:
  pip install -U pip</p>
  
  <p>I get the error message in the Terminal:
  pip: command not found</p>
  
  <p>I have Mac OS 10.14.2, python 3.7.2 and pip 18.1.
  I want to upgrade to pip 19.2.3</p>