Got this error while installing bartendro

[jaysonvalentino]

Traceback (most recent call last):
File "./bartendro_server.py", line 118, in
app.driver.open()
File "/home/pi/Desktop/bartendro/ui/bartendro/router/driver.py", line 173, in open
data = self.ser.read(3)
File "/usr/lib/python2.7/dist-packages/serial/serialposix.py", line 460, in re ad
raise SerialException('device reports readiness to read but returned no data (device disconnected?)')
SerialException: device reports readiness to read but returned no data (device d isconnected?)