OpenCV python Bayer conversion error

The following code:

filePath = os.path.join(root,file)
image = cv2.imread(filePath)
convertedImage = cv2.cvtColor(image, cv2.COLOR_BAYER_GR2RGB)

Produces this error:

opencv\modules\imgproc\src\color.cpp:4196: error: (-215) scn == 1 && dcn == 3 in function cv::cvtColor

What does this error mean (other than stating the number of channels in source and destination)? How can I fix this? Is it to do with the way I load the image?