/usr/lib/python2.7/dist-packages/mercurial/thirdparty/ is in mercurial-common 4.5.3-1ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/python2.7/dist-packages/mercurial/thirdparty/__init__.py
/usr/lib/python2.7/dist-packages/mercurial/thirdparty/attr/
/usr/lib/python2.7/dist-packages/mercurial/thirdparty/attr/__init__.py
/usr/lib/python2.7/dist-packages/mercurial/thirdparty/attr/_compat.py
/usr/lib/python2.7/dist-packages/mercurial/thirdparty/attr/_config.py
/usr/lib/python2.7/dist-packages/mercurial/thirdparty/attr/_funcs.py
/usr/lib/python2.7/dist-packages/mercurial/thirdparty/attr/_make.py
/usr/lib/python2.7/dist-packages/mercurial/thirdparty/attr/converters.py
/usr/lib/python2.7/dist-packages/mercurial/thirdparty/attr/exceptions.py
/usr/lib/python2.7/dist-packages/mercurial/thirdparty/attr/filters.py
/usr/lib/python2.7/dist-packages/mercurial/thirdparty/attr/validators.py
/usr/lib/python2.7/dist-packages/mercurial/thirdparty/selectors2.py