/usr/share/sigil/python3lib/ is in sigil-data 0.9.9+dfsg-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/sigil/python3lib/gencheck.py
/usr/share/sigil/python3lib/metadata_utils.py
/usr/share/sigil/python3lib/metaproc2.py
/usr/share/sigil/python3lib/metaproc3.py
/usr/share/sigil/python3lib/ncxdata.py
/usr/share/sigil/python3lib/ncxgenerator.py
/usr/share/sigil/python3lib/opf2data.py
/usr/share/sigil/python3lib/opf3data.py
/usr/share/sigil/python3lib/opf_newparser.py
/usr/share/sigil/python3lib/sanitycheck.py
/usr/share/sigil/python3lib/updatechecker.py
/usr/share/sigil/python3lib/xmlprocessor.py
/usr/share/sigil/python3lib/xmlsanitycheck.py