[PATCH 4 of 6 V2] py3: implement __bytes__ for committablectx

[Pulkit Goyal]

# HG changeset patch
# User Pulkit Goyal <7895pulkit at gmail.com>
# Date 1496264118 -19800
#      Thu Jun 01 02:25:18 2017 +0530
# Node ID d6d7a160ee30b4296c2750cbf341cc550fe1657f
# Parent  a2c4837cd74f9ff787e4f085a7b216075fcd233e
py3: implement __bytes__ for committablectx

Before this method, calling bytes on workingctx or memctx calls
basectx.__bytes__ since the magic method was not defined for this class. When it
calls the method from basectx class, it returns TypeError because None is passed
into it.

After this commit `hg update -C` works on Python 3 if eol is not enabled.

diff --git a/mercurial/context.py b/mercurial/context.py
--- a/mercurial/context.py
+++ b/mercurial/context.py
@@ -1387,6 +1387,9 @@
     def __str__(self):
         return str(self._parents[0]) + r"+"
 
+    def __bytes__(self):
+        return bytes(self._parents[0]) + "+"
+
     def __nonzero__(self):
         return True