What do I need to change so my tornado code can post successfully?

I have the following (with some strings modified) which works when using the requests library.

import requests
from pprint import pprint
import json

PEM = '/full/path/to/my.pem'

client_id='cliendID'
client_secret='clientSecret'

USER='myuser'
PSWD='mypwd'

url = 'https://theurl.com/request/'
 
data = {
    "grant_type": "password",
    "username": USER,
    "password": PSWD
}

auth = (client_id, client_secret)
response = requests.post( url, auth=auth, data=data, verify=PEM )
answer = response.json()['answer']

print( answer )

The answer printed is what I expect.

The following usage of curl also works:

curl -iv --user cliendID:clientSecret --key /full/path/to/server.key --cert /full/path/to/my.pem -F grant_type=password -F username=myuser -F password=mypwd https://theurl.com/request/

However, when I try to do the same using Tornado and AsyncHTTPClient, I get a "Bad Request" response. Some sample Tornado code is:

from tornado.httpclient import AsyncHTTPClient
from tornado.ioloop import IOLoop
import json

async def get_content():
    PEM = '/full/path/to/my.pem'

    client_id='cliendID'
    client_secret='clientSecret'

    url = 'https://theurl.com/request/'

    USER='myuser'
    PSWD='mypwd'

    data = {
        "grant_type": "password",
        "username": USER,
        "password": PSWD
    }


    bodyData = json.dumps( data )

    http_client = AsyncHTTPClient()
    response = await http_client.fetch( url,
                                        method        = 'POST',
                                        body          = bodyData,
                                        auth_username = client_id,
                                        auth_password = client_secret,
                                        ca_certs      = PEM )

    print( response.body.decode() )



async def main():
    await get_content()



if __name__ == "__main__":
    io_loop = IOLoop.current()
    io_loop.run_sync(main)

If I had to guess, I believe the issue is with how I am sending the bodyData.

What do I need to change in the Tornado code so this will work...?

By default, the requests library and Tornado's AsyncHTTPClient, both, send the body data as form encoded data (i.e. with Content-Type: application/x-www-form-urlencoded).

The requests library automatically encodes the data dict with the correct content type.

But with Tornado's client, you're requried to manually encode the data as follows:

from urllib.parse import urlencode

bodyData = urlencode(data)

...

Cause of the error:

You're getting the Bad Request error because you're sending the data as JSON but the Content-Type header (sent automatically by Tornado) still says www-form-urlencoded. That means the server can't decode your supplied data because it doesn't know that it's JSON.