I can't remember if I had that or not, though I think one install did.
It's almost certainly a combination of bad configuration / bad code in that release, but if you can still get to a console login (CRTL-ALT-F2 etc - unlikely, I suspect, but worth a shot) you could just kill the process so the installation completes, and then fix the config files etc at your leisure.
I expect that I left mine for an hour or so to see if it was ever going to sort itself out, and then just powercycled the Pi if not. Not good as a habit, but the correct thing to do if some POS process is making the machine unusable because it's trying to use an unconnected network etc.
Fixing the SD image IS possible, but may be beyond your ability to manage on your own.
In short: mount the image via loop, and -x /usr/bin/unattended-upgrade.
If that at least mostly made sense to you, GFI - you can find the exact syntax for the mount etc online. If it sounded like gibberish, then your best bet is to just install while on a proper LAN connection, do something else for an hour when it hits that point again (or just leave it overnight), and just power cycle it if it's still not done after that. gl
