Trouble with PyDist files and versioned dependencies

[Christopher Baines <chris@cbaines.net>]

I have a python package that I want to depend on python-lxml (>= 3.3.1).

So, I have put a .pydist file in debian/ containing.
lxml python-lxml (>= 3.3.1)

This gets installed in the package, but the package still has a
unversioned dependency on python-lxml.

Looking at the source code in /usr/share/dh-python/dhpython/pydist.py I
can't quite tell if the functionality described in the documentation [1]
is even implemented, let alone just broken. It simply just seems to only
install the pydist file, and not consult the contents when deciding the
details of the dependencies?

Does anyone know what is going on here, and does anyone know of any
packages that succeed on getting dh_python2 to make versioned dependencies?

Thanks,

Chris

[1] Relevant part of man dh_python2
   dependencies
       dh_python2  tries  to translate Python dependencies from
requires.txt file to Debian dependencies. Use debian/pydist-overrides or
--no-guessing-deps option to over‐
       ride it if the guess is incorrect. If you want dh_python2 to
generate more strict dependencies (f.e. to avoid ABI problems)  create
debian/python-foo.pydist  file.
       See  /usr/share/doc/python-doc/README.PyDist  (provided  by
python-doc package) for more information. If the pydist file contains
PEP386 flag or set of (uscan like)
       rules, dh_python2 will make the depedency versioned (version
requirements are ignored by default).