/usr/bin/depythontex3 is in texlive-extra-utils 2016.20170123-5.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 | #!/bin/sh
if which python3 >/dev/null 2>&1
then
python3 /usr/share/texlive/texmf-dist/scripts/pythontex/depythontex3.py "$@"
else
echo "You need to have python3 installed to be able to use" >&2
echo "the Python 3 version of depythontex!" >&2
echo "Exiting." >&2
fi
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