pycompat: deprecate using bytes

Python2 has been dropped for a while, so lets comply to the signature of the
global function.

This open the way to drop the use of `pycompat.getattr` and company, and,
especially, the associated `util.safehasattr`.

mercurial/pycompat.py

@@ -355,6 +355,13 b' def getdoc(obj: object) -> Optional[byte'
 def _wrapattrfunc(f):
     @functools.wraps(f)
     def w(object, name, *args):
+        if isinstance(name, bytes):
+            from . import util
+
+            msg = b'function "%s" take `str` as argument, not `bytes`'
+            fname = f.__name__.encode('ascii')
+            msg %= fname
+            util.nouideprecwarn(msg, b"6.6", stacklevel=2)
         return f(object, sysstr(name), *args)
 
     return w