AppKernel's inherited Kernel::init() function is depreciated itself so changing it is not a viable long term solution.
You can easily override the error reporting by changing the call to Debug::enable(); in both app/console and web/app_dev.php like so.
Change
Debug::enable();
to
Debug::enable(E_RECOVERABLE_ERROR & ~E_NOTICE & ~E_STRICT & ~E_DEPRECATED, false);
This will leave all other error reporting in tact while suppressing depreciated warnings. And you don't need to mess with the Kernel at all.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…