[Zope] manage_addFile() => TypeError

[Terrel Shumway]

I want to upload a File into a Folder under DTML control

This code
   <dtml-call "manage_addFile(rep.this(),'newid',file)">

where rep is a folder, and file is from <input type='file' name='file'>
produces this error

  Error Type: TypeError
  Error Value: argument 1: expected read-only character buffer,
ImplicitAcquirerWrapper found

Traceback (innermost last):
<snip>
  File E:\opt\z\lib\python\DocumentTemplate\DT_Let.py, line 145, in render
    (Object: newid=get_new_id)
  File E:\opt\z\lib\python\DocumentTemplate\DT_Util.py, line 321, in eval
    (Object: manage_addFile(rep.this(),newid,file))
  File &lt;string&gt;, line 0, in ?
  File E:\opt\z\lib\python\OFS\Image.py, line 115, in manage_addFile
    (Object: ElementWithAttributes)
  File E:\opt\z\lib\python\OFS\Image.py, line 169, in __init__
    (Object: &lt;Folder instance at 00FFD620&gt;)
  File E:\opt\z\lib\python\OFS\Image.py, line 252, in _get_content_type
    (Object: &lt;Folder instance at 00FFD620&gt;)
  File E:\opt\z\lib\python\OFS\content_types.py, line 162, in
guess_content_type
    (Object: ElementWithAttributes)
  File E:\opt\z\bin\lib\mimetypes.py, line 57, in guess_type
    (Object: ElementWithAttributes)
  File E:\opt\z\bin\lib\urllib.py, line 759, in splittype
    (Object: ElementWithAttributes)
  File E:\opt\z\bin\lib\re.py, line 119, in match
TypeError: (see above)


The part I don't understand is in OFS/Image.py, line 252

if type(body) is not type(''): body=body.data
            content_type, enc=guess_content_type(
                getattr(file, 'filename',id), body, content_type)
        return content_type

What is this getattr() that takes three arguments?  My guess is that id is
the default value in 
case 'filename' is not found... no Id should be a string, not an
ImplicitAquirerWrapper. I give up.

I even tried to pass the content type explicitly too, but File.__init__()
still tries to "guess" the content type. 
(why? I suppose mimetypes.guess_type() is smarter than the programmer/user
<g>)

Anyway. I don't care anymore *why* it doesn't work. I want to know what
*will* work. 
I would prefer to use OFS.Image.File (a core component), but I am about
ready to use the FileObject from Confera.

Am I doing something terribly wrong?