Enabling Flask autoescape on files with *jinja2 extension. From http://stackoverflow.com/questions/13222925/how-do-i-enable-autoescaping-in-templates-with-a-jhtml-extension-in-flask

flask_autoescape_extension.py

class JHtmlEscapingFlask(Flask):

    def select_jinja_autoescape(self, filename):
        if filename is None:
            return False
        if filename.endswith('.jinja2'):
            return True
        return Flask.select_jinja_autoescape(self, filename)

app = JHtmlEscapingFlask(__name__)