Detecting changes across two images
The value of :

img1 = imageio.imread(".jpg")


are rgb value ? i mean are they ranged between 0-255 or between 0 and 1. 
Cause if they where all between 0 and 1 then:

((img1 - img2)**2)


will have always value below 10 indeed the maximum value of this operations could be only 1 and therefore the maximum value obtained here :

np.sqrt(squared_diff[:,:,0] + squared_diff[:,:,1] + squared_diff[:,:,2])


could be np.sqrt(3) and that's always minor than 10 and ">10" operator will return an array with all False values