[Bug 82397] Re: Use a more sensible message for "unknown" in permission tab.

[joelbryan]

It's hard to know what the "unknown" message is pertaining to,
a user will think the other way when they saw a word "unknown" on their files, it means that it is an indication that some features are not enabled and some packages are needed to be installed to enable that feature to display those information correctly. It might also mean that the program doesn't know how to display it correctly.

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Use a more sensible message for "unknown" in permission tab.
https://launchpad.net/bugs/82397