[XML-SIG] LookupError: unknown encoding: utf-8 under mod_python

[Rodrigo B. de Oliveira]

<traceback>
    data = context.content.document.toxml('utf-8')

  File "/usr/local/lib/python2.2/site-packages/_xmlplus/dom/minidom.py",
line 40, in toxml
    return self.toprettyxml("", "", encoding)

  File "/usr/local/lib/python2.2/site-packages/_xmlplus/dom/minidom.py",
line 49, in toprettyxml
    writer = codecs.lookup(encoding)[3](writer)

LookupError: unknown encoding: utf-8
</traceback>

environment is:
	* python 2.2.2
	* mod_python 3.0.1
	* apache 2.0.43
	* pyxml 0.8.1

I'm pretty sure that this problem is more related to mod_python than to
pyxml since the same code works just fine when executed from the shell
but maybe you know something about it... Do you?

Thanks in advance,
Rodrigo