OpArrayCache.setInSlot() not working

[burgerdev]

The setInSlot() method of the OpArrayCache class is not working correctly, I suspect because the method _allocateManagementStructures() is not called by default, which leads to _dirtyShape being None.

Workaround is to set the block shape to something different.

from lazyflow.operators.opArrayCache import OpArrayCache
from lazyflow.graph import Graph
import numpy
op = OpArrayCache(graph=Graph())
op.Input.setValue(numpy.zeros((20,20)))
op.Input[0:20,0:20] = numpy.ones((20,20))

Result:

Traceback (most recent call last):
  File "chachetest.py", line 8, in <module>
    op.Input[0:20,0:20] = numpy.ones((20,20))
  File "/home/burger/Private/Coding/hci/lazyflow/lazyflow/slot.py", line 896, in __setitem__
    self.operator.setInSlot(self, (), roi, value)
  File "/home/burger/Private/Coding/hci/lazyflow/lazyflow/operators/opArrayCache.py", line 414, in setInSlot
    blockKey = roiToSlice(blockStart,blockStop)
  File "/home/burger/Private/Coding/hci/lazyflow/lazyflow/roi.py", line 287, in roiToSlice
    return tuple(map(rTsl1,start,stop))
  File "/home/burger/Private/Coding/hci/lazyflow/lazyflow/roi.py", line 269, in <lambda>
    rTsl1 = lambda x,y:slice(x.__int__(),y.__int__())
AttributeError: 'NoneType' object has no attribute '__int__'