Problem: we expect a runtime type of T, but it is instead scala.runtime.Nothing$
Cause: an implicit call to formatsExcept[T : ClassTag] is not filling in the type parameter. Consider
(a) calling formatsExcept[T : ClassTag] explicitly, or
(b) bringing it in scope with implicit val formats = formatsExcept[T]
Common errors:
Problem: we expect a runtime type of T, but it is instead scala.runtime.Nothing$ Cause: an implicit call to formatsExcept[T : ClassTag] is not filling in the type parameter. Consider (a) calling formatsExcept[T : ClassTag] explicitly, or (b) bringing it in scope with implicit val formats = formatsExcept[T]