[PATCH 10 of 10] util: simplify file I/O functions using context managers

[Bryan O'Sullivan]

# HG changeset patch
# User Bryan O'Sullivan <bryano at fb.com>
# Date 1452638975 28800
#      Tue Jan 12 14:49:35 2016 -0800
# Node ID 69a304f8a51acd7c833a2be0d3aadc2c7935d42f
# Parent  e9a844767dfabda6625b15d1f2e6231aefa13e2c
util: simplify file I/O functions using context managers

diff --git a/mercurial/util.py b/mercurial/util.py
--- a/mercurial/util.py
+++ b/mercurial/util.py
@@ -1444,25 +1444,16 @@ def ensuredirs(name, mode=None, notindex
         os.chmod(name, mode)
 
 def readfile(path):
-    fp = open(path, 'rb')
-    try:
+    with open(path, 'rb') as fp:
         return fp.read()
-    finally:
-        fp.close()
 
 def writefile(path, text):
-    fp = open(path, 'wb')
-    try:
+    with open(path, 'wb') as fp:
         fp.write(text)
-    finally:
-        fp.close()
 
 def appendfile(path, text):
-    fp = open(path, 'ab')
-    try:
+    with open(path, 'ab') as fp:
         fp.write(text)
-    finally:
-        fp.close()
 
 class chunkbuffer(object):
     """Allow arbitrary sized chunks of data to be efficiently read from an