sysupdate and space check

[Peter Fraser]

I make a stupid mistake; I didn't check partition sizes before doing a 
sysupgrade.
sysupgrade ran out of space or /usr in the middle of the upgrade.
I know I should have checked first but it would be nice if sysupgrade did warn 
me.
The site was a 20-minute drive away, and their down time was a lot longer then 
I expected.