fix Bytes submission pb on POST, due to multiple call to field.process_form_value for a same field. In the case of file, stream.read() doesn't return file's data the second time (since the cursor is at the end of the file). Fix this by having a generic process_form_value method that cache field's value in form.formvalues[field] and so _process_form_value is only called once. You should then override that later method on custom fields.

doc/book usr/share/doc/cubicweb-documentation
debian/cubicweb-doc usr/share/doc-base/cubicweb-doc