∀ {α : Type u_1} {R : Type u_2} [inst : Monoid R] [inst_1 : DistribMulAction R ENNReal]
  [inst_2 : IsScalarTower R ENNReal ENNReal] {x : MeasurableSpace α} (c : R) (μ : MeasureTheory.Measure α),
  (c • μ).toOuterMeasure = c • μ.toOuterMeasure