Prefer builtin open() over io.open() and codecs.open()

In Python3, the functions io.open() is an alias of the builtin open()
and codecs.open() is functionally equivalent. To reduce indirection,
number of imports, and number of patterns, always prefer the builtin.

https://docs.python.org/3/library/io.html#high-level-module-interface

> io.open()
>
> This is an alias for the builtin open() function.

1 files changed, 1 insertions, 2 deletions

diff --git a/sphinx/util/docutils.py b/sphinx/util/docutils.py
index 547d74c17..96944bd6f 100644
--- a/sphinx/util/docutils.py
+++ b/sphinx/util/docutils.py
@@ -10,7 +10,6 @@
 """
 from __future__ import absolute_import
 
-import codecs
 import os
 import re
 import types
@@ -314,7 +313,7 @@ class SphinxFileOutput(FileOutput):
         # type: (unicode) -> unicode
         if (self.destination_path and self.autoclose and 'b' not in self.mode and
                 self.overwrite_if_changed and os.path.exists(self.destination_path)):
-            with codecs.open(self.destination_path, encoding=self.encoding) as f:
+            with open(self.destination_path, encoding=self.encoding) as f:  # type: ignore
                 # skip writing: content not changed
                 if f.read() == data:
                     return data