import xml.dom.minidom

def show_bug():
    document = '<dom mbid="5">foobar_attributes</dom>'
    dom = xml.dom.minidom.parseString(document)
    attribs = dom.getElementsByTagName('dom')[0].attributes

    if attribs.has_key('mbid'):
        print "This works..  found 'mbid' attribute"

    if 'mbid' in attribs:
        print "Will never get here, the above will throw an exception"