Better error message for calculate_qparams (#26985)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/26985
Produce better error message when `calculate_qparams` doesn't return
something we expect. It should return a Tuple of two tensors.
Test Plan:
ci
Imported from OSS
Differential Revision: D17636252
fbshipit-source-id: 6caee48134f46d2f25dec3fa655e99c15043a67f
