Lazily build error strings in schema matching using replay. (#21241)
Summary:
Saves ~20% (5.3s -> 4.3s) loading DenseNet on my laptop.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21241
Differential Revision: D15590338
fbshipit-source-id: 2c8aebc829d4ea46f358d74d396cc44f5f57fcf5
