Using the default external terminal emulator (konsole), as well as some alternatives (e.g. xfce Terminal), fails with the following error message:

GDB cannot use the tty* or pty* devices
Check the settings on /dev/tty* and /dev/pty*
As root you may need to "chmod ug+rw\" tty* and pty* devices
and/or add the user to the tty group using
"usermod -G tty username". 

Adding my user to tty group does not fix.

Setting ug+rw permissions on /dev/tty* and /dev/pts/* (Fedora does not have /dev/pty*) does not fix.  I even tried o+rw; no dice.

xterm is the only terminal emulator I've found thus far that works (but I dislike using it).

I've also tried xfce Terminal but it fails in the same manner.

Have not tried gnome terminal (don't use gnome and can't get it run for some reason).