issue2551046: Attempts to attach file or create large message fail

under python2

This patch fixes a bug introduced for working around an issue in
python3. There were a few ways to fix this, but I think this fix:

  1) follows the spirit of the original patch
  2) follows python programming expectations

I am still having an issue trying to get both code paths executed from
the test suite. The super code path is not tested, but I did validate
that path from the browser and it works producing valid uploaded files
in both python 2 and 3.

Thanks to Ezio Melotti and Joseph Myers for their help in guiding me
to come up with this solution.

Author: rouilj

roundup/cgi/client.py

@@ -230,7 +230,8 @@ def update(self, set_cookie=False, expire=None):
         if set_cookie:
             self.client.add_cookie(self.cookie_name, self._sid, expire=expire)
 
-class BinaryFieldStorage(cgi.FieldStorage):
+# import from object as well so it's a new style object and I can use super()
+class BinaryFieldStorage(cgi.FieldStorage, object):
     '''This class works around the bug https://bugs.python.org/issue27777.
 
        cgi.FieldStorage must save all data as binary/bytes. This is
@@ -243,7 +244,7 @@ def make_file(self, mode=None):
         import tempfile
         if self.length >= 0:
             return tempfile.TemporaryFile("wb+")
-        return super().make_file()
+        return super(BinaryFieldStorage, self).make_file()
 
 class Client:
     """Instantiate to handle one CGI request.