[PATCH py3] ui: construct _keepalnum list in a python3-friendly way

[Augie Fackler]

# HG changeset patch
# User Augie Fackler <augie at google.com>
# Date 1487262890 18000
#      Thu Feb 16 11:34:50 2017 -0500
# Node ID 791b4e846a7b9a0783440b9504585438777fe2d2
# Parent  1ee685defe80117cf6aafea1ede6c33c478abceb
ui: construct _keepalnum list in a python3-friendly way

It'll be more expensive, but it preserves the behavior.

diff --git a/mercurial/ui.py b/mercurial/ui.py
--- a/mercurial/ui.py
+++ b/mercurial/ui.py
@@ -36,7 +36,12 @@ from . import (
 urlreq = util.urlreq
 
 # for use with str.translate(None, _keepalnum), to keep just alphanumerics
-_keepalnum = ''.join(c for c in map(chr, range(256)) if not c.isalnum())
+if pycompat.ispy3:
+    _unicodes = [bytes([c]).decode('latin1') for c in range(256)]
+    _notalnum = [s.encode('latin1') for s in _unicodes if not s.isalnum()]
+else:
+    _notalnum = [c for c in map(chr, range(256)) if not c.isalnum()]
+_keepalnum = ''.join(_notalnum)
 
 samplehgrcs = {
     'user':