Get the os architecture using rpm --eval

def get_osarch():
    '''
    Get the os architecture using rpm --eval
    '''
    if salt.utils.path.which('rpm'):
        ret = subprocess.Popen(
            'rpm --eval "%{_host_cpu}"',
            shell=True,
            close_fds=True,
            stdout=subprocess.PIPE,
            stderr=subprocess.PIPE).communicate()[0]
    else:
        ret = ''.join([x for x in platform.uname()[-2:] if x][-1:])

    return salt.utils.stringutils.to_str(ret).strip() or 'unknown'