dkms_info fails with exception when parsing modalias

[Robert Liu]

When I ran dkms_info on my machine, it failed with an exception.

Here is the log:
$ /usr/lib/plainbox-provider-checkbox/bin/dkms_info --format json
[000051ms] Started
[000051ms] Querying dkms database
[000065ms] Looking for packages that provide: /usr/src/drm-4.15-4.18.12/dkms.conf
[000112ms] Looking for kernel modules in /var/lib/dkms/drm-4.15/4.18.12/4.15.0-34-generic/x86_64/module
[000113ms] Looking at inserted kernel modules
[000113ms] Inspecting module ttm
[000116ms] Looking for modalias objects matching
[000116ms] Inspecting module backport
[000119ms] Inspecting module chash
[000121ms] Inspecting module i915
[000124ms] Looking for modalias objects matching
[000124ms] Looking for modalias files in /sys/devices
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/guacamole/core.py", line 248, in eat
    return self._dispatch()
  File "/usr/lib/python3/dist-packages/guacamole/core.py", line 298, in _dispatch
    result = ingredient.dispatch(self.context)
  File "/usr/lib/python3/dist-packages/guacamole/ingredients/cmdtree.py", line 152, in dispatch
    return self._dispatch(context, 0)
  File "/usr/lib/python3/dist-packages/guacamole/ingredients/cmdtree.py", line 165, in _dispatch
    retval = command.invoked(context)
  File "/usr/lib/plainbox-provider-checkbox/bin/dkms_info", line 549, in invoked
    dkms_pkg = DkmsPackage(dkms_name, dkms_ver)
  File "/usr/lib/plainbox-provider-checkbox/bin/dkms_info", line 274, in __init__
    self.install_mods = self._list_install_modules()
  File "/usr/lib/plainbox-provider-checkbox/bin/dkms_info", line 345, in _list_install_modules
    install_mods[m] = match_patterns(tuple(aliases))
  File "/usr/lib/plainbox-provider-checkbox/bin/dkms_info", line 137, in match_patterns
    hw_modaliases = get_system_modaliases()
  File "/usr/lib/plainbox-provider-checkbox/bin/dkms_info", line 90, in get_system_modaliases
    (modalias_type, modalias_string) = data.split(":", 1)
ValueError: not enough values to unpack (expected 2, got 1)

Then I found some of modalias files are empty. For instance:
$ cat /sys/devices/LNXSYSTM\:00/LNXSYBUS\:00/INT34D7\:00/modalias
I don't know if it's normal or there is bug with the driver. But I think it would be better to have a check before parsing it.