<rdar://problem/13147878>
Be more user-friendly about not having scripting enabled:
a) if Python was built-out then tell people about it explicitly
b) if we are told to use none as a scripting language, then tell people about that too

This should limit the cases where the semi-cryptic error message "there is no embedded script interpreter in this mode." actually shows

git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@175570 91177308-0d34-0410-b5e6-96231b3b80d8