If it really only one file, include this into the package of your project and just "import" it.

On the other hand side you could as well port the Debian package (http://packages.debian.org/sid/python-beautifulsoup) to Maemo as it would be a nice "to have" along with mechanize ;-)

I did this with python-clientform and python-mechanize. It was not that hard after some help from #python-devel.

You can look into my packages, or into other python-${module} packages to fin out how.

Most likely you only have to add pymaemo-optify to "Depends"
http://maemo.org/packages/view/python-mechanize/
http://maemo.org/packages/view/python-clientform/

Cheers
Bjoern