title: "ERROR: No matching distribution found for numpy" when deploying app to Heroku
body: <p>I'm trying to upload my Dash app to Heroku. I've been following the documentation, however, when I go to push I get the following error:</p>
  <pre><code>  ERROR: Could not find a version that satisfies the requirement numpy==1.20.1
    remote:        ERROR: No matching distribution found for numpy==1.20.1 (from -r      /    t     tmp/build_32b7cf97/requirements.txt (line 19))
    remote:  !     Push rejected, failed to compile Python app.
  </code></pre>
  <p>My version of Python is 3.8 and pip is 21.0.1. Oddly enough, I saw this in the output log as well:</p>
  <pre><code>remote: Building source:
  remote: 
  remote: -----&gt; Building on the Heroku-20 stack
  remote: -----&gt; Python app detected
  remote: -----&gt; Installing python-3.6.12
  remote: -----&gt; Installing pip 20.1.1, setuptools 47.1.1 and wheel 0.34.2
  remote: -----&gt; Installing SQLite3
  remote: -----&gt; Installing requirements with pip
  </code></pre>
  <p>Heroku installed python 3.6 and pip 20.1.1. Could that be related to the problem? I've looked for similar problems by other users and they recommended deleting the offending dependency from the requirements.txt.  But in this case, I need it for my program.</p>
  <p>Any suggestions would be greatly appreciated as I have hit a wall.</p>