Summary:
lit's `OneCommandFileTest` class implements an abstract method that
raises if called. However, it raises by referencing an undefined
symbol. Instead, raise explicitly by throwing a `NotImplementedError`.
This is clearer, and appeases Python linters.
Patch By Brian Gesiak!
Reviewers: ddunbar, echristo, beanz
Subscribers: llvm-commits, mehdi_amini
Differential Revision: https://reviews.llvm.org/D25170
llvm-svn: 283090
54624e7eed