I made one additional change to the patch. Instead of "mcset = part.get_content_charset('us-ascii')", I do "mcset = part.get_content_charset() or 'us-ascii'" as in Decorate.py to allow for charset= with no value.
I made one additional change to the patch. Instead of "mcset = part.get_ content_ charset( 'us-ascii' )", I do "mcset = part.get_ content_ charset( ) or 'us-ascii'" as in Decorate.py to allow for charset= with no value.