It must be possible for demonstrators unfamiliar with the language to quickly achieve such a level that they can help students debug their programs.
I was the course's principal demonstrator and am a relatively experienced Python programmer. However I was assisted by five others, only two of which had encountered Python before. By reading the handbook and being directed to http://www.python.org the demonstrators who were new to Python were quickly (usually within the first day) sufficiently competent that they could solve student problems. Obviously a significant fraction of these problems were not Python-specific (algorithmic misunderstandings, etc.), but those that were (mainly syntax errors) were always quickly solved by the demonstrators (with occasional reference to the handbook). The important conclusion is that demonstrators were quickly able to read Python programs.