Comment 1 for bug 1050638

never late to fix some good oldies
just reorder end lines and move python version checker before response headers

  if sys.version_info[0]>=3:
   # Python 3 support
   if type(output)==str:
    output = bytes(output,charset)
    content_length = str(len(output))

  response_headers += [
   ('Content-Type', "%s; charset=%s" % (content_type,charset)),
   ('Content-Length', content_length)
  ]
  start_response(status, response_headers)

  if hasattr(output,'read'):
   # File-like object
   block_size = 4096
   if 'wsgi.file_wrapper' in environ:
    return environ['wsgi.file_wrapper'](output, block_size)
   else:
    return iter(lambda: output.read(block_size), '')

  return [output]