Twilio authentication always fails

Issue Summary

I am developing a Python (Flask) voice app on a local machine and using Ngrok tunnel to allow Twilio access the app via a webhook (all set up according to the Twilio guide). I need to add a step to check the requests are coming from Twilio and am using the RequestValidator from the Twilio Python SDK. However, this step always returns false, but should be true as I am the one initiating the request during testing.

Steps to Reproduce

1. Set up a test voice application with Python Flask, and using Ngrok tunnel
2. Get the host, request url and scope
3. Run RequestValidator()

Code Snippet

In your Python Flask test voice application, set up a /call app route, then inside the call() test the following

validator = RequestValidator(TWILIO_AUTH_TOKEN)

path = request.path
headers = dict(request.headers)
host = headers.get('Host')
url = f"http://{host}{path}"
body = request.data

validator.validate(request.url, headers, body)

Technical details:

• twilio-python version: 8.1.0
• python version: 3.8.8
• Flask version: 2.2.2
• pyngrok version: 6.0.0

Start with the Flask /call route and the RequestValidator usage shown in the issue, checking how request.url, the Host header, path, and request body are constructed through the Ngrok request. Reproduce the validation result with the listed Python, Flask, and twilio-python versions, then confirm that a genuine test request validates successfully.