WC_Paypal was removed in 2.0 in favour of WC_Gateway_Paypal, this
patch deprecates the original WC_Paypal class & returns an instance
of the WC_Gateway_Paypal object instead of potentially causing a
fatal error.
This line should contain use $response instead of the not existing $result.
The error only occurs when debugging is enabled and the communication with Paypal API failed for some reason. But in this case, it results in a fatal php error: Call to a member function get_error_message() on a non-object