Parse request payload and return POST-vars

		:return: None or dictionary of names and tuples of values

def post_vars(self):
		""" Parse request payload and return POST-vars

		:return: None or dictionary of names and tuples of values
		"""
		if self.method() != 'POST':
			raise RuntimeError('Unable to return post vars for non-get method')

		content_type = self.content_type()
		if content_type is None or content_type.lower() != 'application/x-www-form-urlencoded':
			raise RuntimeError('Unable to return post vars with invalid content-type request')

		request_data = self.request_data()
		request_data = request_data.decode() if request_data is not None else ''
		re_search = WWebRequestProto.post_vars_re.search(request_data)
		if re_search is not None:
			return urllib.parse.parse_qs(re_search.group(1), keep_blank_values=1)