Description of problem:

I ran hp-check --runtime to troubleshoot a scanner problem with a HP Officejet 6110 which I'll likely file another report about. hp-check crashed with the following trace indicating that /usr/include/cups was not found.

Traceback (most recent call last):
  File "/usr/share/hplip/base/utils.py", line 266, in walkFiles
    names = os.listdir(root)
FileNotFoundError: [Errno 2] No such file or directory: '/usr/include/cups'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/share/hplip/base/utils.py", line 268, in walkFiles
    raise StopIteration
StopIteration

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/usr/bin/hp-check", line 861, in <module>
    dep.core.init()
  File "/usr/share/hplip/installer/core_install.py", line 500, in init
    self.check_dependencies(callback)
  File "/usr/share/hplip/installer/core_install.py", line 593, in check_dependencies
    self.have_dependencies[d] = self.dependencies[d][3]()
  File "/usr/share/hplip/installer/core_install.py", line 1139, in check_cups_image
    return check_file("raster.h", "/usr/include/cups")
  File "/usr/share/hplip/installer/dcheck.py", line 108, in check_file
    for w in utils.walkFiles(dir, recurse=True, abs_paths=True, return_folders=False, pattern=f):
RuntimeError: generator raised StopIteration

sudo dnf repoquery --whatprovides /usr/include/cups showed cups-devel-1:2.2.8-5.fc29.i686. After installing cups-devel, I ran hp-check --runtime which crashed with the following trace stating that /usr/include/libusb-1.0 wasn't found.

Traceback (most recent call last):
  File "/usr/share/hplip/base/utils.py", line 266, in walkFiles
    names = os.listdir(root)
FileNotFoundError: [Errno 2] No such file or directory: '/usr/include/libusb-1.0'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/share/hplip/base/utils.py", line 268, in walkFiles
    raise StopIteration
StopIteration

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/usr/bin/hp-check", line 861, in <module>
    dep.core.init()
  File "/usr/share/hplip/installer/core_install.py", line 500, in init
    self.check_dependencies(callback)
  File "/usr/share/hplip/installer/core_install.py", line 593, in check_dependencies
    self.have_dependencies[d] = self.dependencies[d][3]()
  File "/usr/share/hplip/installer/core_install.py", line 936, in check_libusb
    return len(locate_file_contains("libusb.h", '/usr/include/libusb-1.0', 'libusb_init'))
  File "/usr/share/hplip/installer/dcheck.py", line 137, in locate_file_contains
    for w in utils.walkFiles(dir, recurse=True, abs_paths=True, return_folders=False, pattern=f):
RuntimeError: generator raised StopIteration

sudo dnf repoquery --whatprovides /usr/include/libusb-1.0 showed libusbx-devel-0:1.0.22-1.fc29.i686. I installed libusbx-devel, then hp-check --runtime crashed with the following trace stating that /etc/PolicyKit wasn't found.

Traceback (most recent call last):
  File "/usr/share/hplip/base/utils.py", line 266, in walkFiles
    names = os.listdir(root)
FileNotFoundError: [Errno 2] No such file or directory: '/etc/PolicyKit'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/share/hplip/base/utils.py", line 268, in walkFiles
    raise StopIteration
StopIteration

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/usr/bin/hp-check", line 861, in <module>
    dep.core.init()
  File "/usr/share/hplip/installer/core_install.py", line 500, in init
    self.check_dependencies(callback)
  File "/usr/share/hplip/installer/core_install.py", line 593, in check_dependencies
    self.have_dependencies[d] = self.dependencies[d][3]()
  File "/usr/share/hplip/installer/core_install.py", line 1164, in check_policykit
    if check_file('PolicyKit.conf', "/etc/PolicyKit") and check_file('org.gnome.PolicyKit.AuthorizationManager.service', "/usr/share/dbus-1/services"):
  File "/usr/share/hplip/installer/dcheck.py", line 108, in check_file
    for w in utils.walkFiles(dir, recurse=True, abs_paths=True, return_folders=False, pattern=f):
RuntimeError: generator raised StopIteration

sudo dnf repoquery --whatprovides /etc/PolicyKit* didn't show any packages.
Running sudo dnf repoquery -l polkit* | less showed /etc/polkit-1 so /etc/PolicyKit might've been renamed to that.

Version-Release number of selected component (if applicable):
hplip-gui-3.18.6-9.fc29.i686
cups-devel-1:2.2.8-5.fc29.i686
libusbx-devel-0:1.0.22-1.fc29.i686
polkit-0:0.115-2.fc29.i686

How reproducible:
The hp-check crashes occurred each time I tried them.

Steps to Reproduce:
1. hp-check --runtime
2. sudo dnf install cups-devel
3. hp-check --runtime
4. sudo dnf install libusbx-devel
5. hp-check --runtime

Actual results:
hp-check --runtime crashed due to /usr/include/cups, /usr/include/libusb-1.0, and /etc/PolicyKit not being found.

Expected results:
hp-check completes normally with no crashes

Additional info:
hplip 3.18.10 is available according to
https://developers.hp.com/hp-linux-imaging-and-printing/release_notes
I don't see hp-check mentioned in the release notes between 3.18.10 and 3.18.6 though.