py_dom.js : fix bug in __contains__ + improve error reporting in callbacks
py_dom.js : fix bug in __contains__ + improve error reporting in callbacks

olemis/brython,jonathanverner/brython,olemis/brython,olemis/brython,Hasimir/brython,molebot/brython,brython-dev/brython,jonathanverner/brython,Hasimir/brython,Hasimir/brython,Hasimir/brython,molebot/brython,kikocorreoso/brython,kikocorreoso/brython,olemis/brython,brython-dev/brython,molebot/brython,brython-dev/brython,molebot/brython,jonathanverner/brython,jonathanverner/brython,kikocorreoso/brython