/usr/lib/python3/dist-packages/sphinx/builders/ is in python3-sphinx 1.3.6-2ubuntu1.
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/usr/lib/python3/dist-packages/sphinx/builders/__init__.py
/usr/lib/python3/dist-packages/sphinx/builders/applehelp.py
/usr/lib/python3/dist-packages/sphinx/builders/changes.py
/usr/lib/python3/dist-packages/sphinx/builders/devhelp.py
/usr/lib/python3/dist-packages/sphinx/builders/epub.py
/usr/lib/python3/dist-packages/sphinx/builders/gettext.py
/usr/lib/python3/dist-packages/sphinx/builders/html.py
/usr/lib/python3/dist-packages/sphinx/builders/htmlhelp.py
/usr/lib/python3/dist-packages/sphinx/builders/latex.py
/usr/lib/python3/dist-packages/sphinx/builders/linkcheck.py
/usr/lib/python3/dist-packages/sphinx/builders/manpage.py
/usr/lib/python3/dist-packages/sphinx/builders/qthelp.py
/usr/lib/python3/dist-packages/sphinx/builders/texinfo.py
/usr/lib/python3/dist-packages/sphinx/builders/text.py
/usr/lib/python3/dist-packages/sphinx/builders/websupport.py
/usr/lib/python3/dist-packages/sphinx/builders/xml.py