post-partition-magic, the partition table was "funky" - when I got to the 
partition editing part and selected disk druid, it popped up a warning about a 
recursive partition table being defined (the resulting screen made it look 
indeed like that) and I hit "Ignore" (*not* "Cancel") initially and 1 other 
time.  Eventually I got the popup again while trying to create another 
partition, but this time (3rd time overall for this warning dialog) I hit 
cancel instead and generated a traceback (soon to be attached to this bug 
report)

Important to note that on the next boot I hit cancel the first time 
the "recursive partition table warning" dialog popped up and got a notice that 
it'd need to initialize the device, which I agreed to and it did fine, leaving 
an empty partition table, and after that point everything worked fine.