/usr/lib/pyshared/python2.7/sidl/CastException.so is in python-sidl 1.4.0.dfsg-8.2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/pyshared/python2.7/sidl/../../../python2.7/dist-packages/sidl/CastException.so