[Twisted-Python] revert

https://twistedmatrix.com/trac/ticket/9280#comment:7 <https://twistedmatrix.com/trac/ticket/9280#comment:7> introduced a pretty serious regression (tracebacks are no longer printed by twisted.web) - can someone please do the appropriate dance to revert this and reopen the ticket? It looks like the directions need updating for git :-). https://twistedmatrix.com/trac/wiki/ReviewProcess#Revertingachange <https://twistedmatrix.com/trac/wiki/ReviewProcess#Revertingachange> -glyph