wireprotov1server: use binascii.unhexlify

wireprotov1server: use binascii.unhexlify

The "hex" codec doesn't exist in Python 3. We could use
`codecs.decode(h, 'hex_codec')`. But `binascii.unhexlify()`
exists and should work the same on Python 2 and 3.

Differential Revision: https://phab.mercurial-scm.org/D5755

--- a/contrib/python3-whitelist	Wed Jan 30 12:55:44 2019 -0800
+++ b/contrib/python3-whitelist	Wed Jan 30 13:07:20 2019 -0800
@@ -504,6 +504,7 @@
 test-progress.t
 test-propertycache.py
 test-pull-branch.t
+test-pull-bundle.t
 test-pull-http.t
 test-pull-permission.t
 test-pull-pull-corruption.t

--- a/mercurial/wireprotov1server.py	Wed Jan 30 12:55:44 2019 -0800
+++ b/mercurial/wireprotov1server.py	Wed Jan 30 13:07:20 2019 -0800
@@ -7,6 +7,7 @@
 
 from __future__ import absolute_import
 
+import binascii
 import os
 
 from .i18n import _
@@ -344,7 +345,7 @@
       one specific branch of many.
     """
     def decodehexstring(s):
-        return set([h.decode('hex') for h in s.split(';')])
+        return set([binascii.unhexlify(h) for h in s.split(';')])
 
     manifest = repo.vfs.tryread('pullbundles.manifest')
     if not manifest: