[XML-SIG] Trying to validate a document which is not in a file

[Stephane Bortzmeyer]

I'm trying to validate a XML document. It is not in a file (it was received 
from the network) and I do not want to write it on disk just to validate it. 
So, I cannot use parse_resource() and I tried:

import xml.parsers.xmlproc.xmlapp
from xml.parsers.xmlproc import xmlval

class MessageValidator (xml.parsers.xmlproc.xmlapp.ErrorHandler):
...

def validate (text):
    val = xmlval.XMLValidator() 
    val.feed(text)

And it always fail:

Traceback (most recent call last):
  File "validator.py", line 36, in ?
    validate(content)
  File "validator.py", line 26, in validate
    val.feed(text)
  File "/usr/lib/python2.1/site-packages/_xmlplus/parsers/xmlproc/xmlval.py", 
line 45, in feed
    self.parser.feed(data)
  File "/usr/lib/python2.1/site-packages/_xmlplus/parsers/xmlproc/xmlutils.py",
 line 330, in feed
    self.do_parse()
  File "/usr/lib/python2.1/site-packages/_xmlplus/parsers/xmlproc/xmlproc.py", 
line 101, in do_parse
    self.parse_doctype()
  File "/usr/lib/python2.1/site-packages/_xmlplus/parsers/xmlproc/xmlproc.py", 
line 510, in parse_doctype
    p.deref()
UnboundLocalError: local variable 'p' referenced before assignment

Reading the source, I tried to add various assignments such as 
val.current_sysID = "Nothing" but I still get the same mistake.