title: Where is pip.conf in my Mac which Python was installed via Homebrew?
body: <p>I installed Python by Homebrew, it was fine for a long time. After upgrading <code>pip</code> to the latest version, I started to get:</p>
  
  <pre><code>DEPRECATION: The default format will switch to columns in the future. You can use --format=(legacy|columns) (or define a format=(legacy|columns) in your pip.conf under the [list] section) to disable this warning.
  </code></pre>
  
  <p>But I can not find my <code>pip.conf</code> under <code>/etc</code> or <code>/usr/local/etc</code> or <code>$HOME/Library/Application Support/pip</code> or <code>$HOME/.config/pip</code>, where can I find it?</p>