landscape-sysinfo crashes if asked to use an unknown plugin

$ landscape-sysinfo --sysinfo-plugins=Foobar
Traceback (most recent call last):
  File "/usr/bin/landscape-sysinfo", line 22, in <module>
    run(sys.argv[1:], reactor)
  File "/usr/lib/python3/dist-packages/landscape/sysinfo/deployment.py", line 115, in run
    for plugin in config.get_plugins():
  File "/usr/lib/python3/dist-packages/landscape/sysinfo/deployment.py", line 71, in get_plugins
    for plugin_name in plugins]
  File "/usr/lib/python3/dist-packages/landscape/sysinfo/deployment.py", line 71, in <listcomp>
    for plugin_name in plugins]
  File "/usr/lib/python3/dist-packages/twisted/python/reflect.py", line 173, in namedObject
    module = namedModule('.'.join(classSplit[:-1]))
  File "/usr/lib/python3/dist-packages/twisted/python/reflect.py", line 159, in namedModule
    topLevel = __import__(name)
ModuleNotFoundError: No module named 'landscape.sysinfo.foobar'

The --exclude-sysinfo-plugins option works just fine with unknown plugins:
$ landscape-sysinfo --exclude-sysinfo-plugins=Foobar
  System load: 0.03 Processes: 81
  Usage of /home: 0.6% of 19.68GB Users logged in: 1
  Memory usage: 6% IP address for ens3: 192.168.122.47
  Swap usage: 0%

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    https://landscape.canonical.com/