reconstruction: pylint errors

pylint gives the following errors:

************* Module nabu.reconstruction.reconstructor_cuda
nabu/reconstruction/reconstructor_cuda.py:29:35: E0602: Undefined variable 'output_shape' (undefined-variable)
nabu/reconstruction/reconstructor_cuda.py:30:60: E0602: Undefined variable 'output_shape' (undefined-variable)
************* Module nabu.reconstruction.rings_cuda
nabu/reconstruction/rings_cuda.py:54:8: E1123: Unexpected keyword argument 'radios_shape' in method call (unexpected-keyword-arg)
************* Module nabu.reconstruction.rings
nabu/reconstruction/rings.py:28:8: E1120: No value for argument 'radios_shape' in method call (no-value-for-parameter)

Related: !223 (merged)