my MBP is a Mid-2012 Retina, and I have had this issue with both the HP Printer Update 5.0 and 5.1. I successfully ignored the update for a while, but tried today and ended up with the same problem. Here's a step-by-step fix that helped me get back on the road:
The Fix (if this sounds scary, don't do it - find someone who is comfortable with this process to help you):
- Hold the power button until your machine shuts off.
- Hold the 'command' and 'R' keys simultaneously, then start your machine. Wait
for the chimes before you let go.
- You will boot into the recovery partition.
- Open the 'terminal' application (hint: it's in a menu)
- cd /Volumes/'your volume name here'/Library/Extensions (to figure out your volume name, type 'cd /Volumes', then type 'ls' to see the list of available volumes. The one you want to use is the one you normally boot into.
- type 'ls - l' when you are in the Extensions directory of your boot Volume, and confirm that you see the directory 'hp_io_enabler.kext'
- type 'rm -rf hp_io_enabler.kext' this will recursively delete the directory and all contents. the f means 'force'.
- if you like, type 'ls -l' to confirm that the 'lil guy is gone.
- quit the Terminal and reboot your machine to the normal Startup.
- get on with your life!
To hide specific updates in Sierra, right-click (Command click) on the specific update, and select the convenient 'Hide Update' that appears. How easy is that?