BR3028880: Revert to nonfatal, better error message, cleanup
Revert to issuing a nonfatal error (it makes no sense to make it a
fatal error, but it probably makes sense for it to be an error instead
of a warning, especially since a lot of prior versions would crash and
apparently noone noticed.) We might have to revisit this based on
user requirements, and/or provide a method for the user to detect an
existing environment variable (%ifenv?).
Issue a better error message, indicating the nature of the failure.
Simplify the code by just updating the string in "p".
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>