title: Add pip install -c to a requirements.txt file
body: <p>I have a package with a <code>requirements.txt</code> like this:</p>
  <pre><code>PACKAGE_A
  &quot;betterproto[compiler]&quot;
  ...
  </code></pre>
  <p>The problem is that the <code>PACKAGE_A</code> depends on <code>jinja2 &gt; 3 ,&lt; 4</code> but <code>betterproto[compiler]</code> depends on <code>jinja2 &gt; 2 ,&lt; 3</code> .
  I found a solution <a href="https://stackoverflow.com/questions/23969793/setup-py-pip-override-one-of-the-dependencys-sub-dependency-from-requirement">here</a> and according to that, I changed my requirements.txt to this:</p>
  <pre><code>PACKAGE_A
  -c constraints.txt &quot;betterproto[compiler]&quot;
  </code></pre>
  <p>which the <code>constraints.txt</code> is something like this:</p>
  <pre><code>jinja2&gt;3,&lt;4
  </code></pre>
  <p>But when I ran the <code>pip3 install -r requirements.txt</code> successfully, and when I saw the <code>pip list</code> , I found that the <code>betterproto[compiler]' and its dependencies (neither </code>jinja2 &lt; 3<code>nor</code>jinja2 &gt;3`) is not installed.</p>
  <p>I should mention that if I run the single command <code>pip install -c constraints.txt &quot;betterproto[compiler]&quot;</code> everything is ok and it will install <code>betterproto[compiler]</code> with <code>jinja &gt;3</code></p>
  <p>I don't know how to include this command in requirements.txt.</p>