584044 gets rid of the exception
but I think we still need to handle the query string param mapping.
Errors relating to this bug in the log look like this:
./payments-adyen-Mar 27 16:36:27 payments1001 adyen_gateway: Constructing! Creating a new adapter of type: [Adyen]
./payments-adyen-Mar 27 16:36:27 payments1001 adyen_gateway: 79820597:79820576.1 setCountry: Country not set.
./payments-adyen-Mar 27 16:36:27 payments1001 adyen_gateway: Exception setting up GatewayPage with adapter class AdyenAdapter: Invalid Payment Method supplied #0 /srv/www/org/wikimedia/payments/extensions/DonationInterface/gateway_common/gateway.adapter.php(261): AdyenAdapter->defineTransactions() #1 /srv/www/org/wikimedia/payments/extensions/DonationInterface/gateway_common/GatewayPage.php(89): GatewayAdapter->__construct(Array) #2 /srv/www/org/wikimedia/payments/includes/specialpage/SpecialPage.php(565): GatewayPage->execute(NULL) #3 /srv/www/org/wikimedia/payments/includes/specialpage/SpecialPageFactory.php(568): SpecialPage->run(NULL) #4 /srv/www/org/wikimedia/payments/includes/MediaWiki.php(288): SpecialPageFactory::executePath(Object(Title), Object(RequestContext)) #5 /srv/www/org/wikimedia/payments/includes/MediaWiki.php(861): MediaWiki->performRequest() #6 /srv/www/org/wikimedia/payments/includes/MediaWiki.php(524): MediaWiki->main() #7 /srv/www/org/wikimedia/payments/index.php(42): MediaWiki->run() #8 {main}
./payments-adyen-Mar 27 16:36:27 payments1001 adyen_gateway: Redirecting to [https://payments.wikimedia.org/index.php/Donate-error?uselang=en]