title: python pip gives: "no such option: -r"
body: <p>So I just freshly installed python3.7. I've used python 2 for a long time but I needed python 3 for a 
  specific module.</p>
  
  <p>So I tried to install the requirements.txt via <code>py -m pip install -r requirements.txt</code> but when I do, I get the following error:</p>
  
  <pre><code>Usage:
    D:\Python37-32\python.exe -m pip &lt;command&gt; [options]
  
  no such option: -r
  </code></pre>
  
  <p>I dont think my install is broken as I get the same error with python 2 (<code>python -m pip install -r requirements.txt</code>)</p>
  
  <p>pip is also in my path but I use it with <code>py -m pip</code> because I have both python versions 2 and 3 installed on my system and need to make sure I use the correct pip with the correct python version</p>
  
  <p>Why can't I install the requirements.txt and am I getting this error instead?</p>