Used "is" for comparisons with None.

        into the resulting message attachments.

        """

        if isinstance(filename, MIMEBase):

            assert content == mimetype == None

            assert content is None

            assert mimetype is None

            self.attachments.append(filename)

        else:

            assert content is not None

        return mark_safe('\n'.join(output))

    def render_option(self, selected_choices, option_value, option_label):

        if option_value == None:

        if option_value is None:

            option_value = ''

        option_value = force_text(option_value)

        if option_value in selected_choices:

        # Control" header before reverting to using the default cache_timeout

        # length.

        timeout = get_max_age(response)

        if timeout == None:

        if timeout is None:

            timeout = self.cache_timeout

        elif timeout == 0:

            # max-age was set to 0, don't bother caching.

    def render(self, context):

        obj_list = self.target.resolve(context, True)

        if obj_list == None:

        if obj_list is None:

            # target variable wasn't found in context; fail silently.

            context[self.var_name] = []

            return ''

                    # exception message will be in group(2)

                    m = re.match(r'(.*)\.(\w+:.+\s)', exc_msg)

                    # make sure there's a match

                    if m != None:

                    if m is not None:

                        f_name = m.group(1)

                        # check to see if m.group(1) contains the module name

                        if f_name == exception[0].__module__: