from authlib.integrations.requests_client import OAuth1Session

[…]

def do_login(app):
	app.loop.call_soon_threadsafe(login_status_start, app)
	consumer_key = app.consumer_key_input.value
	secret_key = app.secret_key_input.value
	try:
		app.loop.call_soon_threadsafe(refresh_status, app, 'Initiating OAuth session…')
		client = OAuth1Session(consumer_key, secret_key)
		app.loop.call_soon_threadsafe(refresh_status, app, 'Fetching request token…')
		request_token = client.fetch_request_token(request_token_url)
		print('works; continues as normal from here')
		[…]

from authlib.integrations.httpx_client import AsyncOAuth1Client

[…]

async def do_login(app):
	login_status_start(app)
	consumer_key = app.consumer_key_input.value
	secret_key = app.secret_key_input.value
	try:
		refresh_status(app, 'Initiating OAuth session…')
		async with AsyncOAuth1Client(consumer_key, secret_key) as client:
			refresh_status(app, 'Fetching request token…')
			request_token = await client.fetch_request_token(request_token_url)
			print('fails here and returns 403; this text is never printed')
			[…]