Comment # 1 on bug 997294 from Wolfgang Bauer

Just to clarify: this is the .xsession-errors-:0 from a "failed" login attempt?
It gets recreated from scratch each time you login.

This doesn't sound good though:
dbus-update-activation-environment: warning: error sending to systemd:
org.freedesktop.DBus.Error.Spawn.ChildExited: Process org.freedesktop.systemd1
exited with status 1

Apparently something is not started in time (or fails to start).

Does this also happen if you use a different display manager/login screen?
You can change that in /etc/sysconfig/displaymanager, xdm should be installed
by default.