It is a no-op under Ruby 1.8 but Pathname#find raises ENOENT if the
directory doesn't exist under 1.9. But we really shouldn't try to clean
a non-existent keg anyway, and FormulaInstaller will have bailed out
long before the clean step if the keg doesn't exist, so lets just not
even test this condition; the cleaner has its own tests anyway.
Alternatively we can adjust the cleaner to handle this case, but I don't
see much value in that.
n.b. with this, the tests now pass under 1.9.3 (for me), which is nice
because I often run them on that version inadvertently.
Signed-off-by: Jack Nagel <jacknagel@gmail.com>