[2009-04-15 17:53:10,198] ERROR:web-services:[19]:    
_write_data(writer, attrs[a_name].value)
[2009-04-15 17:53:10,198] ERROR:web-services:[20]:   File
"/usr/lib/python2.5/site-packages/oldxml/_xmlplus/dom/minidom.py", line
305, in _write_data
[2009-04-15 17:53:10,199] ERROR:web-services:[21]:     data =
data.replace("&", "&amp;").replace("<", "&lt;")
[2009-04-15 17:53:10,199] ERROR:web-services:[22]: AttributeError:
'NoneType' object has no attribute 'replace'

_write_data dunction should be something like this
def _write_data(writer, data):
    "Writes datachars to writer."
    if data:
        data = data.replace("&", "&amp;").replace("<", "&lt;")
        data = data.replace("\"", "&quot;").replace(">", "&gt;")
        writer.write(data)

Have you tried this with xml.dom.minidom?

Yes I am using xml.dom.minidom

doc.toprettyxml(indent="\t").encode('utf-8')

Here is the full traceback...
[2009-04-16 12:00:03,487] ERROR:web-services:[01]: Exception in call:
Traceback (most recent call last):
[2009-04-16 12:00:03,487] ERROR:web-services:[02]:   File
"/home/hda/tiny/bzrtrunk/latest_released/server/bin/wizard/__init__.py",
line 74, in execute_cr
[2009-04-16 12:00:03,487] ERROR:web-services:[03]:     action_res =
action(self, cr, uid, data, context)
[2009-04-16 12:00:03,488] ERROR:web-services:[04]:   File
"/home/hda/tiny/bzrtrunk/latest_released/addons/base_module_record/wizard/base_module_save.py",
line 113, in _create_module
[2009-04-16 12:00:03,488] ERROR:web-services:[05]:     res_xml =
mod.generate_xml(cr, uid)
[2009-04-16 12:00:03,488] ERROR:web-services:[06]:   File
"/home/hda/tiny/bzrtrunk/latest_released/addons/base_module_record/base_module_record.py",
line 328, in generate_xml
[2009-04-16 12:00:03,488] ERROR:web-services:[07]:     #
vim:expandtab:smartindent:tabstop=4:softtabstop=4:shiftwidth=4:
[2009-04-16 12:00:03,488] ERROR:web-services:[08]:   File
"/usr/lib/python2.5/site-packages/oldxml/_xmlplus/dom/minidom.py", line
47, in toxml
[2009-04-16 12:00:03,488] ERROR:web-services:[09]:     return
self.toprettyxml("", "", encoding)
[2009-04-16 12:00:03,489] ERROR:web-services:[10]:   File
"/usr/lib/python2.5/site-packages/oldxml/_xmlplus/dom/minidom.py", line
59, in toprettyxml
[2009-04-16 12:00:03,489] ERROR:web-services:[11]:    
self.writexml(writer, "", indent, newl, encoding)
[2009-04-16 12:00:03,489] ERROR:web-services:[12]:   File
"/usr/lib/python2.5/site-packages/oldxml/_xmlplus/dom/minidom.py", line
1746, in writexml
[2009-04-16 12:00:03,489] ERROR:web-services:[13]:    
node.writexml(writer, indent, addindent, newl)
[2009-04-16 12:00:03,489] ERROR:web-services:[14]:   File
"/usr/lib/python2.5/site-packages/oldxml/_xmlplus/dom/minidom.py", line
821, in writexml
[2009-04-16 12:00:03,490] ERROR:web-services:[15]:    
node.writexml(writer,indent+addindent,addindent,newl)
[2009-04-16 12:00:03,490] ERROR:web-services:[16]:   File
"/usr/lib/python2.5/site-packages/oldxml/_xmlplus/dom/minidom.py", line
821, in writexml
[2009-04-16 12:00:03,490] ERROR:web-services:[17]:    
node.writexml(writer,indent+addindent,addindent,newl)
[2009-04-16 12:00:03,490] ERROR:web-services:[18]:   File
"/usr/lib/python2.5/site-packages/oldxml/_xmlplus/dom/minidom.py", line
816, in writexml
[2009-04-16 12:00:03,491] ERROR:web-services:[19]:    
_write_data(writer, attrs[a_name].value)
[2009-04-16 12:00:03,491] ERROR:web-services:[20]:   File
"/usr/lib/python2.5/site-packages/oldxml/_xmlplus/dom/minidom.py", line
304, in _write_data
[2009-04-16 12:00:03,491] ERROR:web-services:[21]:     data =
data.replace("&", "&amp;").replace("<", "&lt;")
[2009-04-16 12:00:03,491] ERROR:web-services:[22]: AttributeError:
'NoneType' object has no attribute 'replace'

I have solved this error,
My tag has None value for one attribute.
But python should check for None value in _write_data function.

I'm not able to reproduce the issue. Why don't you submit the unit test
that generates the problem? Thanks

Please see this post.

http://bytes.com/topic/python/answers/25245-minidom-questions

This issue will not move unless somebody provides a unit test for it.

Experiencing this issue too.  It occurs when an xml element contains a blank xmlns attribute, e.g.:

{{{
<element xmlns=""/>
}}}

When toxml() is called on a minidom document with this attribute, the exception occurs.

I am including a simple script that causes this crash.

This following markup creates the mistake as described earlier in the comments

<element xmlns="">
<b class="foo" alt=""/>
</element>

This markup doesn't

<element xmlns="bla">
<b class="foo" alt=""/>
</element>

It returns

<?xml version="1.0" ?><element xmlns="bla">
<b alt="" class="foo"/>
</element>

When using this markup

<element bar="">
<b class="foo" alt=""/>
</element>

It outputs the right markup,

<?xml version="1.0" ?><element bar="">
<b alt="" class="foo"/>
</element>

So the mistake occurs really when xmlns="".  I have checked and the following markup is a conformant markup according to the XML specification so xmlns="" or bar="" are conformant on the root element.

<element xmlns="">
<b class="foo" alt=""/>
</element>

XML Namespaces are defined in another specification. http://www.w3.org/TR/REC-xml-names/. In the section of Namespaces default http://www.w3.org/TR/REC-xml-names/#defaulting, The specification is clear.

"The attribute value in a default namespace declaration MAY be empty. This has the same effect, within the scope of the declaration, of there being no default namespace."

the proposed "if data:" earlier in the comment solves the issue. I have attached a unit testcase as required by Mark Lawrence (BreamoreBoy)

Thanks for the test case, committed the fix and the new test in r85546.