python setuptools usage in trac package

[Gunnar Thielebein <gunnar_thielebein@gmx.net>]

I am currently on packaging trac package from the sid repository to the
current version for debian and ubuntu. The sid package is trac-0.11.2.1.

The rule's file contains this line:

>         python setup.py install \
>                 --root=$(CURDIR)/debian/trac \
>                 --single-version-externally-managed
>

When i packaged this version to ubuntu jaunty  which uses python2.6 as
default python version
the installation prefix changed from /usr to /usr/local for unknown reason.

> byte-compiling
> /root/Trac-0.11.4/debian/trac/usr/local/lib/python2.6/dist-packages/trac/resource.py
> to resource.pyc
> byte-compiling
> /root/Trac-0.11.4/debian/trac/usr/local/lib/python2.6/dist-packages/trac/db/pool.py
> to pool.pyc
> byte-compiling
> /root/Trac-0.11.4/debian/trac/usr/local/lib/python2.6/dist-packages/trac/db/mysql_backend.py
> to mysql_backend.pyc
> byte-compiling
> /root/Trac-0.11.4/debian/trac/usr/local/lib/python2.6/dist-packages/trac/db/schema.py
> to schema.pyc
> byte-compiling
> /root/Trac-0.11.4/debian/trac/usr/local/lib/python2.6/dist-packages/trac/db/api.py
> to api.pyc
> byte-compiling
> /root/Trac-0.11.4/debian/trac/usr/local/lib/python2.6/dist-packages/trac/db/postgres_backend.py
> to postgres_backend.pyc
> byte-compiling
> /root/Trac-0.11.4/debian/trac/usr/local/lib/python2.6/dist-packages/trac/db/sqlite_backend.py
> to sqlite_backend.pyc
> byte-compiling
> /root/Trac-0.11.4/debian/trac/usr/local/lib/python2.6/dist-packages/trac/db/util.py
> to util.pyc
> byte-compiling
> /root/Trac-0.11.4/debian/trac/usr/local/lib/python2.6/dist-packages/trac/db/__init__.py
> to __init__.pyc
> byte-compiling
> /root/Trac-0.11.4/debian/trac/usr/local/lib/python2.6/dist-packages/trac/loader.py
> to loader.pyc

For workaround I set the --prefix argument. What I am wonder about, is
it good practice to statically define the prefix in the rules file like
this? Are there documented changes in python's package tools pycentral,
python-shared for python2.6? Are there alternative solution to this?

>         python setup.py install \
>                 --prefix=/usr
>                 --root=$(CURDIR)/debian/trac \
>                 --single-version-externally-managed
>

Best Regards,
Gunnar