puppetlabs/facter — pull request #690 by ffrank (2014-06-04 18:52:26+00:00)
Title: Ticket/facter 2/fact 484 virtual avoid permission warnings

Retrieving the virtual fact without root privileges would yield
warning messages due to missing permissions on
/sys/firmware/dmi/entries/1-0/raw (at least on certain versions of Debian).

The readable? query makes more sense than exists? at this point, anyway.