Persistent Warning: "Multiple packages failed to uninstall." : <p>I have a warning message that came to dinner but now won't leave.</p>

<blockquote>
  <p>Multiple packages failed to uninstall. Restart Visual Studio to finish the process.</p>
</blockquote>

<p><a href="https://i.stack.imgur.com/T8Qui.png" rel="noreferrer"><img src="https://i.stack.imgur.com/T8Qui.png" alt="enter image description here"></a></p>

<p>Unfortunately, however, restarting Visual Studio has no effect—the warning remains.</p>

<p>I've tried cleaning the solution as well as the project; all of my projects' assembly references are intact. I've also issued an <code>Update-Package -Reinstall</code> command—which succeeded—to no avail.</p>

<p>How can I set about fixing this?</p>
