tinfoil: fix get_recipe_file() to return an error on invalid recipe
This function calls cooker.findBestProvider() but didn't handle the fact
that that function returns a tuple (None, None, None, None) when there
is no matching recipe. (This fixes devtool in OpenEmbedded showing a
traceback when an invalid recipe is specified instead of a proper error
message.)
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>