title: Error of "Command 'pip' not found" when trying to install requirements.txt
body: <p>I'm trying to do: pip install -r requirements.txt on an AWS server. I recently pulled a git commit.</p>
  
  <p>I get this error:</p>
  
  <pre><code>Command 'pip' not found, but can be installed with:
  
  sudo apt install python-pip
  </code></pre>
  
  <p>So I tried entering:</p>
  
  <pre><code>sudo apt install python-pip install -r requirements.txt
  
  and then
  
  sudo apt install python-pip -r requirements.txt
  </code></pre>
  
  <p>But both attempts gave me this error:</p>
  
  <pre><code>E: Command line option 'r' [from -r] is not understood in combination with the other options.
  </code></pre>
  
  <p>What is the correct command to install this? Thank you.</p>