The translations that are used when the game tries to get a block or item from a name id are
There error messages are shown for nearly any command including the /setblock command.
The /testforblock command is an exception because it uses a different translation:
This is pretty inconsistent and not needed as the other error message could be used instead.
In 1.11 the translation commands.setblock.notFound is still used but only if the parse block is null which is never the case anymore because if a block with that name does not exist an exception with the translation commands.give.block.notFound is thrown.