XML RPC changes between 3.7 and 3.9 yield 401 http error

[lucas]

Following our previous discussion:
     https://www.talkend.net/post/287193.html

I finally took time (thanks to Florian R.) to get a reproducible example 
of my problem, as asked previously by ChrisA.

The following code is implementing a webserver with Flask, and a client 
with the XMLRPC client:

     import sys
     from xmlrpc import server, client
     from urllib.parse import urlencode
     from flask import Flask, request


     PORT = 23456
     USER, PASSWD = 'user', 'password'
     URL = '127.0.0.1:' + str(PORT)

     if len(sys.argv) > 1 and sys.argv[1] == 'server':
         app = Flask(__name__)
         @app.route('/', methods=['POST'])
         @app.route('/RPC2', methods=['POST'])
         def login():
             print('REQUEST:', request.args)
             return 'ok'
         app.run(debug=True, host='localhost', port=PORT)

     else:
         url = 'http://' + URL + '?' + urlencode({'u': USER, 'p': PASSWD})
         print(url)
         proxy = client.ServerProxy(url)
         print(proxy, dir(proxy))
         print(proxy.add(2, 3))


You can run the client with `python3 p.py`, and the server with `python3 
p.py server`.

On debian, Python 3.7, i got:

     lucas at debianserver:~$ python3.7 p.py server
      * Serving Flask app "p" (lazy loading)
      * Environment: production
        WARNING: This is a development server. Do not use it in a 
production deployment.
        Use a production WSGI server instead.
      * Debug mode: on
      * Running on http://localhost:23456/ (Press CTRL+C to quit)
      * Restarting with stat
      * Debugger is active!
      * Debugger PIN: 249-992-288
     127.0.0.1 - - [27/Mar/2021 18:31:13] "POST /?u=user&p=password 
HTTP/1.1" 404 -


On Arch, python 3.9, i got:

      aluriak at arch❯ python3.9 p.py server
      * Serving Flask app "p" (lazy loading)
      * Environment: production
        WARNING: This is a development server. Do not use it in a 
production deployment.
        Use a production WSGI server instead.
      * Debug mode: on
      * Running on http://localhost:23456/ (Press CTRL+C to quit)
      * Restarting with stat
      * Debugger is active!
      * Debugger PIN: 821-276-100
     127.0.0.1 - - [27/Mar/2021 18:35:45] "POST /RPC2 HTTP/1.1" 200 -


Both systems return the same output on command `pip3 freeze | grep 
Flask`, which is `Flask==1.1.2`.


Note that the two outputs differs in two ways:

     127.0.0.1 - - [27/Mar/2021 18:31:13] "POST /?u=user&p=password 
HTTP/1.1" 404 -
     127.0.0.1 - - [27/Mar/2021 18:35:45] "POST /RPC2 HTTP/1.1" 200 -

The first contains the arguments, and the second contains the path. 
Sounds like there is something wrong with both modules.

This should be a reproducible example ; plus i'm not the only one to 
encounter that problem:
     https://github.com/kynan/dokuwikixmlrpc/issues/8#issuecomment-808755244

Best regards,
--lucas