pyhesiodfs should use Python-Depends for dependencies on other Python modules

[broder]

As per the python-support policy, we should be using Python-Depends instead of just Depends for dependencies on other Python modules:

From /usr/share/doc/python-support/README.gz:

If you're depending on another python module, you should not declare
it in the Depends field, but like this:
        Python-Depends: python-bar (>= some.version)
The appropriate dependencies on python2.X-bar will automatically be
added.

Of course, support for this was only added to dh_pysupport in version 0.6.0, which isn't in Etch, so this fix will have to wait until Etch is deprecated.

See also r24238

[andersk]

In later python-support, that paragraph in the README was clarified with the following restriction:

If you're including public modules or extensions *and* if some other
packages are expected to need them for a specific (non-default) Python
version, you can also add the field:
        Provides: ${python:Provides}

However, if you do that, you need to be very careful. Especially, if
you're depending on another python module, you should not declare it in
the Depends field, but like this:
        Python-Depends: python-bar (>= some.version)
The appropriate dependencies on python2.X-bar will automatically be
added.

This doesn’t particularly matter for pyhesiodfs, since we are neither building nor depending a python2.X-foo package. (Maybe it’s a good idea anyway for consistency, but it’s not worth, e.g., desupporting Etch early or anything.)