Fix literal string in binary context

In 1a26f9b26c, all strings in the context of regexes and
comparisons have been converted to byte-like objects for python2/3
compatibility reasons. This has not been considered in the later
commit 5c54557350, which makes layout2layout break with
TypeError: can't concat str to bytes.

lib/scripts/layout2layout.py

@@ -471,7 +471,7 @@ def convert(lines, end_format):
               re_trimEndLabelString, re_trimLabelCounter):
                 m = r.match(lines[i])
                 if m:
-                    lines[i] = m.group(1) + '"' + m.group(2) + '"'
+                    lines[i] = m.group(1) + b'"' + m.group(2) + b'"'
             i += 1
             continue