/usr/lib/python2.7/doc/tools/whichlibs is in python-old-doctools 2.5.5-2.1.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 | #!/bin/sh
sed -n 's%^\\input{\(lib[a-zA-Z0-9_]*\)}.*%../lib/\1.tex%p' ../lib/lib.tex
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