/usr/lib/python2.7/dist-packages/sage/ext/ is in sagemath-common 8.1-7ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/python2.7/dist-packages/sage/ext/__init__.py
/usr/lib/python2.7/dist-packages/sage/ext/ccobject.h
/usr/lib/python2.7/dist-packages/sage/ext/cdefs.pxi
/usr/lib/python2.7/dist-packages/sage/ext/cplusplus.pxd
/usr/lib/python2.7/dist-packages/sage/ext/fast_callable.pxd
/usr/lib/python2.7/dist-packages/sage/ext/fast_eval.pxd
/usr/lib/python2.7/dist-packages/sage/ext/interpreters/
/usr/lib/python2.7/dist-packages/sage/ext/interpreters/__init__.py
/usr/lib/python2.7/dist-packages/sage/ext/interpreters/wrapper_cc.h
/usr/lib/python2.7/dist-packages/sage/ext/interpreters/wrapper_cc.pxd
/usr/lib/python2.7/dist-packages/sage/ext/interpreters/wrapper_cdf.h
/usr/lib/python2.7/dist-packages/sage/ext/interpreters/wrapper_cdf.pxd
/usr/lib/python2.7/dist-packages/sage/ext/interpreters/wrapper_el.h
/usr/lib/python2.7/dist-packages/sage/ext/interpreters/wrapper_el.pxd
/usr/lib/python2.7/dist-packages/sage/ext/interpreters/wrapper_py.pxd
/usr/lib/python2.7/dist-packages/sage/ext/interpreters/wrapper_rdf.pxd
/usr/lib/python2.7/dist-packages/sage/ext/interpreters/wrapper_rr.h
/usr/lib/python2.7/dist-packages/sage/ext/interpreters/wrapper_rr.pxd
/usr/lib/python2.7/dist-packages/sage/ext/memory_allocator.pxd
/usr/lib/python2.7/dist-packages/sage/ext/mod_int.h
/usr/lib/python2.7/dist-packages/sage/ext/mod_int.pxd
/usr/lib/python2.7/dist-packages/sage/ext/solaris_fixes.h
/usr/lib/python2.7/dist-packages/sage/ext/stdsage.pxd
/usr/lib/python2.7/dist-packages/sage/ext/stdsage.pxi