It turned out to be that scaffold for singeleton resource will always depend on another model, and it's not possible at the moment to make the application tests pass after generate the singeleton scafold. So, it would be better to remove it for now and probably provide another generator, such as singeleton_scaffold, in which also require the depended model name.

[#4863 state:resolved]

Signed-off-by: José Valim <jose.valim@gmail.com>