The RCSB website now compresses XML files.

def retrieve_xml(pdb_id, silent = True):
    '''The RCSB website now compresses XML files.'''
    xml_gz = retrieve_file_from_RCSB(get_rcsb_files_connection(), "/download/%s.xml.gz" % pdb_id, silent = silent)
    cf = StringIO.StringIO()
    cf.write(xml_gz)
    cf.seek(0)
    df = gzip.GzipFile(fileobj = cf, mode='rb')
    contents = df.read()
    df.close()
    return contents