rror</a> must be done at most once.</p>
<p>Completing a future with an error indicates that an exception was thrown
while trying to produce a value.</p>
<p>The <code>error</code> must not be <code>null</code>.</p>
<p>If <code>error</code> is a <code>Future</code>, the future itself is used as the error value.
If you want to complete with the result of the future, you can use:</p>
<pre class="language-dart"><code>thisCompleter.complete(theFuture)
</code></pre>
<p>or if you only want to handle an error from t