py3: provide (del|get|has|set)attr wrappers that accepts bytes

py3: provide (del|get|has|set)attr wrappers that accepts bytes

These functions will be imported automagically by our code transformer.

getattr() and setattr() are widely used in our code. We wouldn't probably
want to rewrite every single call of getattr/setattr. delattr() and hasattr()
aren't that important, but they are functions of the same kind.

--- a/mercurial/pycompat.py	Sun Aug 14 12:44:13 2016 +0900
+++ b/mercurial/pycompat.py	Sun Aug 14 12:51:21 2016 +0900
@@ -31,8 +31,22 @@
 
 if sys.version_info[0] >= 3:
     import builtins
+    import functools
     builtins.xrange = range
 
+    def _wrapattrfunc(f):
+        @functools.wraps(f)
+        def w(object, name, *args):
+            if isinstance(name, bytes):
+                name = name.decode(u'utf-8')
+            return f(object, name, *args)
+        return w
+
+    delattr = _wrapattrfunc(builtins.delattr)
+    getattr = _wrapattrfunc(builtins.getattr)
+    hasattr = _wrapattrfunc(builtins.hasattr)
+    setattr = _wrapattrfunc(builtins.setattr)
+
 stringio = io.StringIO
 empty = _queue.Empty
 queue = _queue.Queue