<p>I think the Issue has been cleared. I think</p>

<pre><code>nametrans = lambda foldername: re.sub ('^\[gmail\]', 'bak',
                               re.sub ('sent_mail', 'sent',
                               re.sub ('starred', 'flagged',
                               re.sub (' ', '_', foldername.lower()))))
</code></pre>

<p>and</p>

<pre><code>folderfilter = lambda foldername: foldername not in '[Gmail]/All Mail'
</code></pre>

<p>were contradicting thus resulting in the error.</p>

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