virt-install hangs at boot menu on RHEL 7

Today was yak shaving the virt-install environment from RHEL 6 to RHEL 7

We auto create a custom ISO for virt-install to consume and point to the kickstart server. We use the serial console for everything

On RHEL 6, we can see the BIOS / syslinux boot menu confirming to boot from the ISO

On RHEL 7, we just get a blank screen...

Many hours of determining if the contents of the ISO created on RHEL 6 can work on RHEL 7, and googling just about every combination of virt-install, hang, RHEL 7, CentOS, and RTFM virt-install, I saw a new flag to virt-install on RHEL 7

--boot menu=on,useserial=on
Enable the bios boot menu, and enable sending bios text output over serial console.

And we instantly see the boot menu dialog, and back to normal building!

Leaving this here for anyone else having issues seeing the boot menu over serial