Because the put happens in a different thread, the message will be printed, but the response will not be recorded correctly.
This was while using replace.py on wikis where I'm not autoconfirmed.
valhallasw@maeglin:pywikibot-core$ python pwb.py version master 0 Pywikibot: [https] wikimedia-pywikibot-core (07aac69, g5912, 2015/07/05, 17:04:33, OUTDATED) Release version: 2.0b3 requests version: 2.2.1 cacerts: /etc/ssl/certs/ca-certificates.crt certificate test: ok Python: 2.7.6 (default, Jun 22 2015, 17:58:13) [GCC 4.8.2] unicode test: ok PYWIKIBOT2_DIR: Not set PYWIKIBOT2_DIR_PWB: PYWIKIBOT2_NO_USER_CONFIG: Not set Config base dir: /home/valhallasw/src/pywikibot-core Usernames for family "wikipedia": en: valhallasw (no sysop configured) Usernames for family "wikitech": en: Merlijn van Deen (no sysop configured) Usernames for family "wiktionary": zh-min-nan: valhallasw (no sysop configured) Usernames for family "commons": commons: valhallasw (no sysop configured)