Comment 4 for bug 1899264

It looks like a python versioning issue. I could install the plugin by running this command:

    python3 /usr/bin/hp-plugin -i

Then, the hp-setup tool encountered another error:

=================
HP Linux Imaging and Printing System (ver. 3.20.3)
Printer/Fax Setup Utility ver. 9.0

Copyright (c) 2001-18 HP Development Company, LP
This software comes with ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to distribute it
under certain conditions. See COPYING file for more details.

Searching... (bus=usb, search=(None), desc=0)
Traceback (most recent call last):
  File "/usr/share/hplip/ui5/setupdialog.py", line 1304, in NextButton_clicked
    self.showAddPrinterPage()
  File "/usr/share/hplip/ui5/setupdialog.py", line 710, in showAddPrinterPage
    self.findPrinterPPD()
  File "/usr/share/hplip/ui5/setupdialog.py", line 789, in findPrinterPPD
    self.print_ppd = cups.getPPDFile2(self.mq, self.model, self.ppds)
  File "/usr/share/hplip/prnt/cups.py", line 491, in getPPDFile2
    family_class=getFamilyClassName(model)
  File "/usr/share/hplip/prnt/cups.py", line 181, in getFamilyClassName
    family_type= dict[m]['family-class']
KeyError: 'family-class'

Done.
=================

This only seems to happen if the program is started with the gui. Running it in interactive mode did not cause any errors, and I could finally use my printer:

    python3 /usr/bin/hp-setup -i