py3: replace bytes[n] with bytes[n:n + 1] in patch.py where needed

mercurial/patch.py

@@ -1693,7 +1693,7 b' def pathtransform(path, strip, prefix):'
                              (count, strip, path))
         i += 1
         # consume '//' in the path
-        while i < pathlen - 1 and path[i] == '/':
+        while i < pathlen - 1 and path[i:i + 1] == '/':
             i += 1
         count -= 1
     return path[:i].lstrip(), prefix + path[i:].rstrip()
@@ -1788,7 +1788,7 b' def scanpatch(fp):'
             else:
                 lr.push(fromfile)
             yield 'file', header
-        elif line[0] == ' ':
+        elif line[0:1] == ' ':
             yield 'context', scanwhile(line, lambda l: l[0] in ' \\')
         elif line[0] in '-+':
             yield 'hunk', scanwhile(line, lambda l: l[0] in '-+\\')