See: https://github.com/edx/XBlock/pull/338 and https://github.com/Pylons/webob/pull/197#issuecomment-200908897 Update whatsnew-1.6 to include a better explanation.
See: https://github.com/edx/XBlock/pull/338 and #197 (comment)
Update whatsnew-1.6 to include a better explanation.