From what I have just said, x.content is a string, not a binary. Therefore the else-block of this code will run.
Well actually the manual says the following about GetHttpRequestData().content:
Raw content from form submitted by client, in string or binary format. For content to be considered string data, the FORM request header "CONTENT_TYPE" must start with "text/" or be special case "application/x-www-form-urlencoded". Other types are stored as a binary object.
This does not seem to work, at least not in my case.
And by the way, the if block is executed in my code as you can see from the names of the files being written (unfortunately empty).