Hello Bernhard, 

I tried to a POST of JPEG file, through urllib2 (which internally uses httplib) and goes through the code that you pointed out and I don't face any problem. I am able to POST binaries using httplib.

I am also surprised at UnicodeDecodeError which is being raised. The POST data is string (8-bit strings) in Python2.7 and the portion of code will have no problem in creating the content.

You will get UnicodeDecodeError, only if you explicitly pass a Unicode Object as Data and never when you pass string or binary string.

Perhaps mechanize is doing something wrong here and sending a Unicode object.

So, this really does not look like a bug to me.

(Also a note on patch. The patch tries to silence the error, which is wrong thing to do).

If you can provide a simple snippet to reproduce this error, feel free reopen this again. I am closing this as 'works for me'.

Thanks.