Render the body of the message from a template. The plain
        body will be rendered from a template named ``plain`` or 
        ``plain + '.txt'`` (in that order of preference). The rich 
        body will be rendered from ``rich`` if given, or else from 
        ``plain + '.html'``. If neither exists, then the message will
        have no rich body.

def render_template(self, plain, rich = None, **context):
        '''Render the body of the message from a template. The plain
        body will be rendered from a template named ``plain`` or 
        ``plain + '.txt'`` (in that order of preference). The rich 
        body will be rendered from ``rich`` if given, or else from 
        ``plain + '.html'``. If neither exists, then the message will
        have no rich body.'''
        self.plain = render_template([plain, plain + '.txt'], **context)
        if rich is not None:
            self.rich = render_template(rich, **context)
        else:
            try:
                self.rich = render_template(plain + '.html', **context)
            except TemplateNotFound:
                pass