policy: mark all string literals as sysstr or bytes

The policy module won't be imported early in future, which means string
literals will be processed by our Python 3 loader.

mercurial/policy.py

@@ -1,49 +1,49 b''
 # policy.py - module policy logic for Mercurial.
 #
 # Copyright 2015 Gregory Szorc <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 from __future__ import absolute_import
 
 import os
 import sys
 
 # Rules for how modules can be loaded. Values are:
 #
 #    c - require C extensions
 #    allow - allow pure Python implementation when C loading fails
 #    cffi - required cffi versions (implemented within pure module)
 #    cffi-allow - allow pure Python implementation if cffi version is missing
 #    py - only load pure Python modules
 #
 # By default, require the C extensions for performance reasons.
 policy = b'c'
 policynoc = (b'cffi', b'cffi-allow', b'py')
 policynocffi = (b'c', b'py')
 
 try:
     from . import __modulepolicy__
     policy = __modulepolicy__.modulepolicy
 except ImportError:
     pass
 
 # PyPy doesn't load C extensions.
 #
 # The canonical way to do this is to test platform.python_implementation().
 # But we don't import platform and don't bloat for it here.
-if '__pypy__' in sys.builtin_module_names:
-    policy = 'cffi'
+if r'__pypy__' in sys.builtin_module_names:
+    policy = b'cffi'
 
 # Our C extensions aren't yet compatible with Python 3. So use pure Python
 # on Python 3 for now.
 if sys.version_info[0] >= 3:
     policy = b'py'
 
 # Environment variable can always force settings.
 if sys.version_info[0] >= 3:
-    if 'HGMODULEPOLICY' in os.environ:
-        policy = os.environ['HGMODULEPOLICY'].encode('utf-8')
+    if r'HGMODULEPOLICY' in os.environ:
+        policy = os.environ[r'HGMODULEPOLICY'].encode(r'utf-8')
 else:
-    policy = os.environ.get('HGMODULEPOLICY', policy)
+    policy = os.environ.get(r'HGMODULEPOLICY', policy)