'Use HTMLParser.get_starttag_text to find which quote delimiter was used
in this tag.
:return: The context instance, one of:
* HtmlAttrDoubleQuote
* HtmlAttrSingleQuote
* HtmlAttrBackticks'

def get_attr_value_context(self, attr_name, attr_value):

    full_tag_text = self.get_starttag_text()
    full_tag_text = self.unescape(full_tag_text)
    all_contexts = [HtmlAttrDoubleQuote, HtmlAttrSingleQuote]
    for context_klass in all_contexts:
        attr_match = ('%s%s%s' % (context_klass.ATTR_DELIMITER, attr_value, context_klass.ATTR_DELIMITER))
        if (attr_match in full_tag_text):
            return context_klass(self.payload, attr_name, self.untidy(attr_value))
    if (attr_value.startswith(HtmlAttrBackticks.ATTR_DELIMITER) and attr_value.endswith(HtmlAttrBackticks.ATTR_DELIMITER)):
        return HtmlAttrBackticks(self.payload, attr_name, self.untidy(attr_value))
    return HtmlAttrNoQuote(self.payload, attr_name, self.untidy(attr_value))
