mail/pyzor: Fix runtime with Python 3.9

Partial patch of
https://github.com/SpamExperts/pyzor/commit/7afe0aedc320dd2689bfbf45e97fdb09adb89686

PR: 265237 [1]
Reported by: Jakob Stoklund Olesen <swig.morning0d@icloud.com> [1]
Reported by: Andrew <andrew@tekrealm.net>