py3: add a r'' prefix to prevent transformer from adding b''

# skip-blame as only r'' prefix was added

Differential Revision: https://phab.mercurial-scm.org/D2356

hgext/convert/monotone.py

@@ -85,7 +85,7 b' class monotone_source(common.converter_s'
             return self.mtnrunsingle(*args, **kwargs)
 
     def mtnrunsingle(self, *args, **kwargs):
-        kwargs['d'] = self.path
+        kwargs[r'd'] = self.path
         return self.run0('automate', *args, **kwargs)
 
     def mtnrunstdio(self, *args, **kwargs):