Cannot read GPIO

Hi, I am trying to use DHT11 and I can read the values by using python script. However, I cannot use the Home assistant as I see the below error. I am using pi 3. Can anyone help to resolve this please?

16-06-20 10:53:22 homeassistant.components.sensor: Error while setting up platform dht
Traceback (most recent call last):
  File "/usr/local/lib/python3.4/dist-packages/homeassistant/helpers/entity_component.py", line 98, in _setup_platform
    discovery_info)
  File "/usr/local/lib/python3.4/dist-packages/homeassistant/components/sensor/dht.py", line 61, in setup_platform
    dev.append(DHTSensor(data, variable, unit, name))
  File "/usr/local/lib/python3.4/dist-packages/homeassistant/components/sensor/dht.py", line 81, in __init__
    self.update()
  File "/usr/local/lib/python3.4/dist-packages/homeassistant/components/sensor/dht.py", line 100, in update
    self.dht_client.update()
  File "/usr/local/lib/python3.4/dist-packages/homeassistant/util/__init__.py", line 289, in wrapper
    result = method(*args, **kwargs)
  File "/usr/local/lib/python3.4/dist-packages/homeassistant/components/sensor/dht.py", line 125, in update
    self.pin)
  File "/home/pi/.homeassistant/deps/Adafruit_DHT/common.py", line 90, in read_retry
    humidity, temperature = read(sensor, pin, platform)
  File "/home/pi/.homeassistant/deps/Adafruit_DHT/common.py", line 77, in read
    return platform.read(sensor, pin)
  File "/home/pi/.homeassistant/deps/Adafruit_DHT/Raspberry_Pi_2.py", line 34, in read
    raise RuntimeError('Error accessing GPIO. Make sure program is run as root with sudo!')
RuntimeError: Error accessing GPIO. Make sure program is run as root with sudo!

sudo adduser hass_user gpio

i have installed home-assistant manually according the documentation on this site in a virtual environment on raspbian and had to use:

sudo adduser homeassistant gpio