'Raise an exception when backend returns certain errors.
Error codes returned from the backend have to be examined
individually. Not all of them are fatal. For example, lun attach
failing becase the client is already attached is not a fatal error.
:param response: a response dict result from the vmemclient request'

def _check_error_code(self, response):

    if ('Error:    0x9001003c' in response['msg']):
        pass
    elif ('Error:    0x9002002b' in response['msg']):
        pass
    elif ('Error:    0x09010023' in response['msg']):
        raise exception.ViolinBackendErr(message=response['msg'])
    elif ('Error:    0x09010048' in response['msg']):
        raise exception.ViolinBackendErr(message=response['msg'])
    elif ('Error:    0x90010022' in response['msg']):
        raise exception.ViolinBackendErrExists()
    elif ('Error:    0x90010089' in response['msg']):
        raise exception.ViolinBackendErr(message=response['msg'])
    else:
        raise exception.ViolinBackendErr(message=response['msg'])
