Comment 5 for bug 1979036

The test failed with error list below:
-----[ Identify what service is managing each physical network interface ]------
ID: com.canonical.certification::net_if_management
Category: com.canonical.plainbox::uncategorised
... 8< -------------------------------------------------------------------------
Traceback (most recent call last):
  File "/tmp/nest-q6kekfja.85214daceec20cd8651bf53a569971cc3a614b158baeaeabe09973416fbf3505/net_if_management.py", line 199, in <module>
    main()
  File "/tmp/nest-q6kekfja.85214daceec20cd8651bf53a569971cc3a614b158baeaeabe09973416fbf3505/net_if_management.py", line 188, in main
    results = identify_managers(has_netplan=is_netplan_available(),
  File "/tmp/nest-q6kekfja.85214daceec20cd8651bf53a569971cc3a614b158baeaeabe09973416fbf3505/net_if_management.py", line 97, in identify_managers
    wired = get_network_interfaces('NETWORK')
  File "/tmp/nest-q6kekfja.85214daceec20cd8651bf53a569971cc3a614b158baeaeabe09973416fbf3505/net_if_management.py", line 39, in get_network_interfaces
    output = sp.check_output(cmd, shell=True).decode(sys.stdout.encoding)
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xc0 in position 38854: invalid start byte