Trivial; make the error message just a pinch more explicit in case we
trip this by accident in the future.
Signed-off-by: John Snow <jsnow@redhat.com>
Message-Id: <20210216021809.134886-12-jsnow@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>