Portable Python script across Python version

commands.getoutput has been move to subprocess module in Python3

Differential Revision: https://reviews.llvm.org/D55205

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@349503 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed