py3: use r'' to prevent the addition of b'' by transformer
There are cases in opts handling in debugcommands.py where we don't need to
convert opts keys back to bytes as there are some handful cases and no other
function using opts value. Using r'', we prevent the transformer to add
a b'' which will keep the value str.
test-convert-git.t
test-subrepo-git.t
test-patchbomb-tls.t