Comment 29 for bug 1309535

The correct way to fix this issue is not to comment out the lines mentioning kwallet, but to make the modules silent by prepending a '-' (dash) to each line. Example:

# /etc/pam.d/lightdm
-auth optional pam_kwallet.so
-auth optional pam_kwallet5.so
-session optional pam_kwallet.so auto_start
-session optional pam_kwallet5.so auto_start

Same in /etc/pam.d/lightdm-greeter.

This feature is mentioned in the pam.conf(5) manpage:

If the type value from the list above is prepended with a - character
the PAM library will not log to the system log if it is not possible to
load the module because it is missing in the system. This can be useful
especially for modules which are not always installed on the system and
are not required for correct authentication and authorization of the
login session.