For PR797:

For PR797:
Adjust usage of the ExecuteAndWait function to use the last argument which
is the ErrMsg string. This is necessitated because this function no longer
throws exceptions on error.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@29791 91177308-0d34-0410-b5e6-96231b3b80d8