Copyright for python-pex source package in Bookworm

Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
Upstream-Name: pex
Source: https://pypi.python.org/pypi/pex

Files: *
Copyright: Copyright 2014 Pants project contributors (see CONTRIBUTORS.md).
License: Apache-2.0

Files: debian/*
Copyright: 2015 Barry A. Warsaw
License: Apache-2.0

License: Apache-2.0
 On Debian-based systems the full text of the Apache 2.0 license can be found
 at /usr/share/common-licenses/Apache-2.0