Fix `git llvm` script when no arguments are supplied on Python 3
Fix `git llvm` script when no arguments are supplied on Python 3

Instead of displaying a help message, it was issuing an error message:

  AttributeError: 'Namespace' object has no attribute 'func'

https://bugs.python.org/issue16308 has more information on the bug.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@367320 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm