fix error response of push API (fixes #2698).
fix error response of push API (fixes #2698).

C-nakajima/OpenPNE3,upsilon/travis-test,C-nakajima/OpenPNE3,kashiwasan/symfony-advanced,upsilon/travis-test,ShinichiU/OpenPNE3,isaosano/OpenPNE3,ShinichiU/OpenPNE3,nishizoe/OpenPNE3,kashiwasan/symfony-advanced,isaosano/OpenPNE3,isaosano/OpenPNE3,C-nakajima/OpenPNE3,isaosano/OpenPNE3,ShinichiU/OpenPNE3,C-nakajima/OpenPNE3,ShinichiU/OpenPNE3,nishizoe/OpenPNE3