Fetching Python news headlines for Alexa
You probably want to move the session to a global variable(or simply use requests.get) else at function level it is not helping in re-using any connections right now and is adding an extra level of indentation to your code.
This is mostly opinionated but grouping from x import y based imports below import z makes the imports bit easier to read. Plus keep the items within each group sorted as well.  Google's style guide also contains a related example.

import requests
from bs4 import BeautifulSoup
from dateutil.parser import parse
from flask import Flask, jsonify
from lxml import etree
from nltk import sent_tokenize