Pluggable authentication modules are the core of user authentication in any
modern linux distribution.

Modules pam_passwdqc and pam_ecryptfs were removed between OL6 and OL7,
thus making some PAM configuration files no longer valid.

Preupgrade assistant will comment out these modules in your PAM configuration
files after the in-place upgrade automatically, but you should review and
regain the authentication functionality other way, if these modules were
required for your authentication policy.
