After building & installing hplip-3.17.6 on Slackware 14.2, cannot run hp-check or hp-toolbox

I've been trying to install hplip-3.17.6 on Slackware 14.2 (64bit). It builds and installs okay (with a good share of warnings...), but when I try to run either 'hp-check' or 'hp-toolbox', I get errors:
$ hp-check
warning: CUPSEXT could not be loaded. Please check HPLIP installation.
$ hp-toolbox
Traceback (most recent call last):
  File "/usr/local/bin/hp-toolbox", line 41, in <module>
    from base import status, tui, module
  File "/usr/local/share/hplip/base/status.py", line 33, in <module>
    import cupsext
ImportError: No module named cupsext

After extracting the files from hplip-3.17.6.run file, I configure using the following options:
./configure --with-hpppddir=/usr/share/ppd/HP --prefix=/usr/local --enable-qt4 --disable-libusb01_build --enable-doc-build --enable-scan-build --enable-cups-ppd-install --disable-foomatic-drv-install --disable-foomatic-ppd-install --disable-hpijs-install --disable-udev_sysfs_rules --disable-policykit --disable-cups-drv-install --enable-hpcups-install --enable-network-build --enable-dbus-build --enable-scan-build --enable-fax-build
Then, I did 'make' followed by 'sudo make install'. Then I tried to run 'hp-check' and 'hp-toolbox' and got the errors listed above.

Since I don't know python, and don't feel safe hacking python code, I've been looking for workarounds and/or advice.

Any suggestions? Am I building it incorrectly (and if so, what configure options do you suggest...)? Do I need to set environment symbols for Python?
BTW, I use hplip on a Ubuntu distro and when I searched for 'cupsext' (locate cupext) on a Ubuntu partition, I find '/usr/lib/python3/dist-packages/cupsext.cpython-35m-x86_64-linux-gnu.so', but could find no similar python module on the Slackware partiton... Do I need to install more python stuff on my Slackware distribution?? Also, I've successfully built & used hplip tools on earlier Slackware releases using earlier hplip releases.

Other system info:
$ uname -a
Linux werz2 4.9.31 #2 SMP Wed Jun 7 15:09:05 CDT 2017 x86_64 Intel(R) Core(TM) i7-5500U CPU @ 2.40GHz GenuineIntel GNU/Linux
$ python --version
Python 2.7.13
$ ls /usr/lib64/python2.7
(622 python files + 26 subdirectories)

Thanks!