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, 2 insertions, 3 deletions

diff --git a/sphinx/ext/autosummary/generate.py b/sphinx/ext/autosummary/generate.py
index dbadfe8d5..b4b8bcc42 100644
--- a/sphinx/ext/autosummary/generate.py
+++ b/sphinx/ext/autosummary/generate.py
@@ -20,7 +20,6 @@
 from __future__ import print_function
 
 import argparse
-import codecs
 import locale
 import os
 import pydoc
@@ -249,8 +248,8 @@ def find_autosummary_in_files(filenames):
     """
     documented = []  # type: List[Tuple[unicode, unicode, unicode]]
     for filename in filenames:
-        with codecs.open(filename, 'r', encoding='utf-8',  # type: ignore
-                         errors='ignore') as f:
+        with open(filename, 'r', encoding='utf-8',  # type: ignore
+                  errors='ignore') as f:
             lines = f.read().splitlines()
             documented.extend(find_autosummary_in_lines(lines, filename=filename))
     return documented