Grab a single image from the Xeoma web server

            Arguments:
                image_name: the name of the image to fetch (i.e. image01)
                username: the username to directly access this image
                password: the password to directly access this image

async def async_get_camera_image(self, image_name, username=None, password=None):
        """
            Grab a single image from the Xeoma web server

            Arguments:
                image_name: the name of the image to fetch (i.e. image01)
                username: the username to directly access this image
                password: the password to directly access this image
        """

        try:
            data = await self.async_fetch_image_data(
                image_name, username, password)
            if data is None:
                raise XeomaError('Unable to authenticate with Xeoma web '
                                 'server')
            return data
        except asyncio.TimeoutError:
            raise XeomaError('Connection timeout while fetching camera image.')
        except aiohttp.ClientError as e:
            raise XeomaError('Unable to fetch image: {}'.format(e))