title: why can't I install watchman using brew command?
body: <p>I'm trying to run a react native app and I've been told I need to download &quot;watchman&quot;.
  When I tried to run the command <code>brew install watchman</code> it gave this error:</p>
  <pre><code>Error: The following formula cannot be installed from bottle and must be
  built from source.
    python@3.9
  Install the Command Line Tools for Xcode 11.3.1 from:
    https://developer.apple.com/download/more/
  </code></pre>
  <p>Do I need to install Xcode or I'm just missing something? Is there any easier way to install watchman?</p>
  <p>Thank you in advance.</p>