title: write python black reformat on vim buffer :!black % and :e working in one step
body: <p>I want (<strong>without any vim plugging</strong>) run <code>black</code> on my vim buffer in one step.</p>
  <p>So editing some Python code in vim.</p>
  <p>I only get to have it working in two steps:</p>
  <p>step 1:</p>
  <pre><code>:!black %
  </code></pre>
  <p>step 2 (to reload the buffer):</p>
  <pre><code>:e
  </code></pre>
  <p>Note this is not working:</p>
  <pre><code>:!black % |e
  </code></pre>