Comment # 2 on bug 943312 from Dr. Werner Fink

(In reply to Stephan Kulow from comment #1)

Because this one is a plymouth problem?  Also systemd-vconsole-setup.service
can not write as long as plymouth is locking down virtual consoles.

To fix plymouth add

     BuildRequires:  systemd >= 186

in the spec file, then systemd-ask-password-plymouth.service should show a
correct executable with full path like

     ExecStart=/usr/bin/systemd-tty-ask-password-agent --watch --plymouth