size-check: warn if blocker tracker bugs not found
    
    This is towards #14 - for F33, image size bugs which should have
    been set as release blockers were not. I really can't figure out
    why not, but this should at least narrow things down a bit if it
    happens again for F34...
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>