py3: use `%d` for int in % formatting

On Python 3, `%s` is an alias to `%b`, which requires that the object implements
`__bytes__()`, which is not the case for `int`.

hgext/convert/subversion.py

@@ -773,7 +773,7 b' class svn_source(converter_source):'
         self.convertfp.flush()
 
     def revid(self, revnum, module=None):
-        return b'svn:%s%s@%s' % (self.uuid, module or self.module, revnum)
+        return b'svn:%s%s@%d' % (self.uuid, module or self.module, revnum)
 
     def revnum(self, rev):
         return int(rev.split(b'@')[-1])