The window with the image Opencv 3.1.0 python 2.7 does not close, how to fix it?

Question

Python

The window with the image Opencv 3.1.0 python 2.7 does not close, how to fix it?
I do

cv2.imshow('image',img)
cv2.waitKey(0)
cv2.destroyAllWindows()

but the window won't close