py3: add b'' to make a triple quoted string bytes on Python 3

Transformer does not adds b'' in front of triple quoted strings to prevent
converting docs to bytes.

mercurial/util.py

@@ -1168,7 +1168,7 b' def copyfiles(src, dst, hardlink=None, p'
 
     return hardlink, num
 
-_winreservednames = '''con prn aux nul
+_winreservednames = b'''con prn aux nul
     com1 com2 com3 com4 com5 com6 com7 com8 com9
     lpt1 lpt2 lpt3 lpt4 lpt5 lpt6 lpt7 lpt8 lpt9'''.split()
 _winreservedchars = ':*?"<>|'