Discrepancy in the information and IPN sample code

[sonus21]

In the dev doc IPN verification URL is described as follows

Send response messages back to PayPal:
https://ipnpb.sandbox.paypal.com/cgi-bin/webscr (for Sandbox IPNs)
https://ipnpb.paypal.com/cgi-bin/webscr (for live IPNs)

But in the code

It's used from one of the following

VERIFY_URL_PROD = 'https://www.paypal.com/cgi-bin/webscr'
VERIFY_URL_TEST = 'https://www.sandbox.paypal.com/cgi-bin/webscr'

[overint]

The URLs in the code were/are the old URLs, which still work for backward compatibility however I have changed them over to the new URLs.
Thanks for the flag.

[sonus21]

As per the doc, the sample code still seems to be inconsistent, we've to add User-Agent as well in the code.

[overint]

I have created a new issue for updating the samples to send a user agent, thanks.