Change to correct import (hopefully)
@@ -3,7 +3,7 @@ import numpy as np
import astropy.io.fits as fits
import astropy.units as u
from astropy.coordinates import Angle
-from gammapy.cube import PSFKernel
+from .psf_kernel import PSFKernel
from gammapy.irf import EnergyDependentTablePSF
from gammapy.maps import Map
