Quando tento enviar uma imagem com urllib2, ocorre a exceção UnicodeDecodeError.

Corpo da postagem HTTP:

f = open(imagepath, "rb")
binary = f.read()
mimetype, devnull = mimetypes.guess_type(urllib.pathname2url(imagepath))

body = """Content-Length: {size}
Content-Type: {mimetype}

{binary}
""".format(size=os.path.getsize(imagepath),  
           mimetype=mimetype,
           binary=binary)

request = urllib2.Request(url, body, headers)
opener = urllib2.build_opener(urllib2.HTTPSHandler(debuglevel=1))
response = opener.open(request)
print response.read()

Traceback:

   response = opener.open(request)
  File "/usr/local/lib/python2.7/urllib2.py", line 404, in open
    response = self._open(req, data)
  File "/usr/local/lib/python2.7/urllib2.py", line 422, in _open
    '_open', req)
  File "/usr/local/lib/python2.7/urllib2.py", line 382, in _call_chain
    result = func(*args)
  File "/usr/local/lib/python2.7/urllib2.py", line 1222, in https_open
    return self.do_open(httplib.HTTPSConnection, req)
  File "/usr/local/lib/python2.7/urllib2.py", line 1181, in do_open
    h.request(req.get_method(), req.get_selector(), req.data, headers)
  File "/usr/local/lib/python2.7/httplib.py", line 973, in request
    self._send_request(method, url, body, headers)
  File "/usr/local/lib/python2.7/httplib.py", line 1007, in _send_request
    self.endheaders(body)
  File "/usr/local/lib/python2.7/httplib.py", line 969, in endheaders
    self._send_output(message_body)
  File "/usr/local/lib/python2.7/httplib.py", line 827, in _send_output
    msg += message_body
  File "/home/usertmp/biogeek/lib/python2.7/encodings/utf_8.py", line 16, in decode
    return codecs.utf_8_decode(input, errors, True)
UnicodeDecodeError: 'utf8' codec can't decode byte 0xff in position 49: invalid start byte

python versão 2.7.5

Alguém sabe uma solução para isso?