When detecting numpy, assign relavant variables outside the try block (#20739)
Summary:
When detecting the presence of NumPy using import, move numpy-related variable assignments outside the try block (i.e., to an else block) to improve readability.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20739
Differential Revision: D15453916
Pulled By: ezyang
fbshipit-source-id: d3c37f2b290846be3c6a1462251cbb3e95d493be
