/usr/lib/ is in python-egenix-mxstack 3.2.1-1ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/python2.7/
/usr/lib/python2.7/dist-packages/
/usr/lib/python2.7/dist-packages/mx/
/usr/lib/python2.7/dist-packages/mx/Stack/
/usr/lib/python2.7/dist-packages/mx/Stack/mxStack/
/usr/lib/python2.7/dist-packages/mx/Stack/mxStack/mxStack.so
/usr/lib/pyshared/
/usr/lib/pyshared/python2.7/
/usr/lib/pyshared/python2.7/mx/
/usr/lib/pyshared/python2.7/mx/Stack/
/usr/lib/pyshared/python2.7/mx/Stack/mxStack/
/usr/lib/python2.7/dist-packages/mx/Stack/mxStack/__init__.py
/usr/lib/python2.7/dist-packages/mx/Stack/mxStack/test.py
/usr/lib/python2.7/dist-packages/mx/Stack/UserStack.py
/usr/lib/python2.7/dist-packages/mx/Stack/__init__.py
/usr/lib/python2.7/dist-packages/mx/Stack/stackbench.py
/usr/lib/pyshared/python2.7/mx/Stack/mxStack/mxStack.so