For the debugging purpose, I want to invoke the GTK failed dialog.
In Ubuntu, I can find the binary at /usb/lib/gnome-session/gnome-session-failed. Is the same function executable available in Fedora? I tried to search around but could not find it in the system.
You can check files in a rpm package this way:
$ rpm -ql gnome-session | grep failed
/usr/lib/systemd/user/gnome-session-failed.service
/usr/lib/systemd/user/gnome-session-failed.target
/usr/libexec/gnome-session-failed
Seems for the version you are using there was not such executable and the fail dialog would run by doing : gnome-session whale.
See: https://github.com/GNOME/gnome-session/blob/e59b938c644a78236fd5ed9d708022be3b990ddc/gnome-session/main.c#L296
gnome-session-failed is not available in the version you mentioned.
you need to use gnome-session instead and specify with -whale.