It seems that fresh new hplip - package or hp-setup package has an error ?
Because in earlier time it was no problem to install driver for HP LaserJet Pro 200 (M251n)
with hp-setup.
error output of hp-setup is as follows ... (it seems to be a python-error ?) ...

solus@home ~ $ sudo hp-setup

HP Linux Imaging and Printing System (ver. 3.18.6)
Printer/Fax Setup Utility ver. 9.0

Copyright (c) 2001-15 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.

QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-root'
Searching... (bus=usb, search=(None), desc=0)
Traceback (most recent call last):
File "/usr/share/hplip/ui5/setupdialog.py", line 1305, in NextButton_clicked
self.showAddPrinterPage()
File "/usr/share/hplip/ui5/setupdialog.py", line 711, in showAddPrinterPage
self.findPrinterPPD()
File "/usr/share/hplip/ui5/setupdialog.py", line 790, in findPrinterPPD
self.print_ppd = cups.getPPDFile2(self.mq, self.model, self.ppds)
File "/usr/share/hplip/prnt/cups.py", line 492, in getPPDFile2
family_class=getFamilyClassName(model)
File "/usr/share/hplip/prnt/cups.py", line 182, in getFamilyClassName
family_type= dict[m]['family-class']
KeyError: 'family-class'
Abgebrochen

    Is this because of hyphen in python-code below ? At variable
    getFamilyClassName resp. family_type or family-class ?

    I just installed HPLIP through the Software Center, which did did show any error massages, which maybe I would have seen if I had installed through the command line. It appears to be working fine for me as well.

    dschinn1001 make sure your system is fully up-to-date sudo eopkg up
    Hplip hasn't been updated for a while.

      hello Kyrios - system is up-to-date with Version 4.0 - but when I recall, is that hplip in earlier version 1 year ago - had no bugs with this model of HP LaserJet Pro 200 (M251n) - could be that yesterday the server of HP was down somehow ?! Or the Blackhat from Hamburg is interfering somehow ?! I check again next hours ...

        I've been meaning to look at this and I haven't tried hp-setup on my solus vm yet. I know the current shipping version of hplip has issues with later releases of Python 3.7 but I note solus is still on 3.6 so this should be fine. If I get a moment at home I'll test this with my printer.

          kyrios what's the reason? Do new versions require a later version of Python?

          I meant to say, hplip 3.18.6 has issues with python 3.7. The issue with hplip versions above 3.18.6 is that they contain closed source blobs. Debian patch them out and this same patch is used in the current versions of hplip that ship with both Fedora and Arch.

              dschinn1001 hp-setup is working fine for me - no errors. You shouldn't need to run this as root by the way (ie. drop the sudo).

              You could also try running # hp-setup -i to avoid running the GUI.

                Justin - Hey ?! Dont worry about my health ... The health of this BlackHat Hacker is more in danger than mine.