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Pywikibot: [https] wikimedia-pywikibot-core (07aac69, g5912, 2015/07/05, 17:04:33, OUTDATED)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)