Bug#684432: SELinux is the Reason

[Anton Martchukov]

Based on IRC discussion the reason was identified to be
pam_selinux.so plugged through /etc/pam.d/gdm3-autologin
that produces:

gdm-welcome][5739]: DEBUG(+): GdmSessionWorker: received
pam message of type 2 with payload 'Would you like to enter
a security context? [N]  '

interactive prompt. On my system selinux is in permissive
mode. gdm loaded fine after I relabeled file systems.

-- 
Anton Martchukov
http://www.martchukov.com