FWIW, I get the same error trying to sideload via adb.
So I got the update to push through and install but my device got soft bricked and boot looped :-/ Ended up factory resetting and installing the 4.3 system image via adb. Oh well. Weekend project now to reinstall my apps and get my home screens the way I like them again....thank god I backed up my apps to my Google Drive a few weeks ago via Titanium Backup...
Remember to go to play store and make the apps not automatically update. 4.3 default is auto updates.