stringutil: ast.literal_eval needs a unicode on py3

Fortunately for us, this is really only used internally, so we can be
lazy about the encoding here.

test-wireproto-framing.py now passes on Python 3.

Differential Revision: https://phab.mercurial-scm.org/D3368

contrib/python3-whitelist

@@ -437,4 +437,5 b' test-username-newline.t'
 test-verify.t
 test-websub.t
 test-win32text.t
+test-wireproto-framing.py
 test-xdg.t

mercurial/utils/stringutil.py

@@ -510,4 +510,6 b' def parsebool(s):'
 def evalpythonliteral(s):
     """Evaluate a string containing a Python literal expression"""
     # We could backport our tokenizer hack to rewrite '' to u'' if we want
+    if pycompat.ispy3:
+        return ast.literal_eval(s.decode('latin1'))
     return ast.literal_eval(s)