Hello,
This is a known issue with SimpleITK and Slicer in debug mode.
When Slicer is compiled in debug mode, it still compiles Python in release mode. There are only a couple libraries which link against Python and the Slicer run time. These are compiles in different modes Debug and Release. SimpleITK lacks the creative code that is in VTK which defines certain preprocessor definitions before including the Python header to mix Release and Debug libraries.
I even have a prototype branch to add the hack to SimpleITK:
If someone is willing continue work on the patch and help with this Slicer specific customization in SimpleITK, that would be wonderful.
-Brad