title: Homebrew pyenv... can't install Python 3.8.3, despite I already have it installed
body: <p>I have 3.8.2 installed via pyenv but I want to upgrade to 3.8.3 on my local machine, to match the version we're using in production.</p>
  
  <pre><code>$  pyenv install 3.8.3
  python-build: definition not found: 3.8.3
  
  The following versions contain `3.8.3' in the name:
    miniconda-3.8.3
    miniconda3-3.8.3
  
  See all available versions with `pyenv install --list'.
  
  If the version you need is missing, try upgrading pyenv:
  
    brew update &amp;&amp; brew upgrade pyenv
  </code></pre>
  
  <p>ok let's try that...</p>
  
  <pre><code>$  brew update &amp;&amp; brew upgrade pyenv
  Updating Homebrew...
  Warning: pyenv 1.2.18 already installed
  </code></pre>
  
  <p>I'm unclear where the Python versions that pyenv installs from are provided.  I already have 3.8.3 installed:</p>
  
  <pre><code>$  brew info python@3.8
  python@3.8: stable 3.8.3 (bottled) [keg-only]
  Interpreted, interactive, object-oriented programming language
  https://www.python.org/
  /usr/local/Cellar/python@3.8/3.8.2 (4,137 files, 63.0MB)
    Poured from bottle on 2020-04-21 at 11:47:57
  From: https://github.com/Homebrew/homebrew-core/blob/master/Formula/python@3.8.rb
  ==&gt; Dependencies
  Build: pkg-config ✔
  Required: gdbm ✔, openssl@1.1 ✔, readline ✔, sqlite ✘, xz ✔
  ==&gt; Caveats
  Python has been installed as
    /usr/local/opt/python@3.8/bin/python3
  
  You can install Python packages with
    /usr/local/opt/python@3.8/bin/pip3 install &lt;package&gt;
  They will install into the site-package directory
    /usr/local/Cellar/python@3.8/3.8.3/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages
  
  See: https://docs.brew.sh/Homebrew-and-Python
  
  python@3.8 is keg-only, which means it was not symlinked into /usr/local,
  because this is an alternate version of another formula.
  
  ==&gt; Analytics
  install: 398,535 (30 days), 966,259 (90 days), 1,270,935 (365 days)
  install-on-request: 11,428 (30 days), 29,656 (90 days), 42,309 (365 days)
  build-error: 0 (30 days)
  </code></pre>
  
  <p>So it's not that 3.8.3 is not available in Homebrew.  And my Homebrew "linked" Python is 3.7.7, but that didn't stop me from installing 3.8.2.</p>
  
  <p>Are we just stuck waiting for pyenv to push a new release to Homebrew?  Is there some way I can point pyenv to my existing Homebrew-installed 3.8.3?</p>