Replace codecs.open with open

Since Python 3, using codecs.open() is unnecessary as the builtin
supports an encoding argument. Use the simpler and more conventional
pattern.

The default mode for open() is 'r', so redundant arguments have been
removed.

The argument newline='' was added to FileOpener to preserve line endings
when modifying a file.

codespell_lib/_codespell.py

@@ -17,7 +17,6 @@
 """
 
 import argparse
-import codecs
 import configparser
 import fnmatch
 import os
@@ -172,7 +171,7 @@ def open(self, filename):
 
     def open_with_chardet(self, filename):
         self.encdetector.reset()
-        with codecs.open(filename, 'rb') as f:
+        with open(filename, 'rb') as f:
             for line in f:
                 self.encdetector.feed(line)
                 if self.encdetector.done:
@@ -181,7 +180,7 @@ def open_with_chardet(self, filename):
         encoding = self.encdetector.result['encoding']
 
         try:
-            f = codecs.open(filename, 'r', encoding=encoding)
+            f = open(filename, encoding=encoding, newline='')
         except UnicodeDecodeError:
             print("ERROR: Could not detect encoding: %s" % filename,
                   file=sys.stderr)
@@ -205,7 +204,7 @@ def open_with_internal(self, filename):
             elif not self.quiet_level & QuietLevels.ENCODING:
                 print("WARNING: Trying next encoding %s"
                       % encoding, file=sys.stderr)
-            with codecs.open(filename, 'r', encoding=encoding) as f:
+            with open(filename, encoding=encoding, newline='') as f:
                 try:
                     lines = f.readlines()
                 except UnicodeDecodeError:
@@ -463,19 +462,19 @@ def parse_ignore_words_option(ignore_words_option):
 
 
 def build_exclude_hashes(filename, exclude_lines):
-    with codecs.open(filename, mode='r', encoding='utf-8') as f:
+    with open(filename, encoding='utf-8') as f:
         for line in f:
             exclude_lines.add(line)
 
 
 def build_ignore_words(filename, ignore_words):
-    with codecs.open(filename, mode='r', encoding='utf-8') as f:
+    with open(filename, encoding='utf-8') as f:
         for line in f:
             ignore_words.add(line.strip())
 
 
 def build_dict(filename, misspellings, ignore_words):
-    with codecs.open(filename, mode='r', encoding='utf-8') as f:
+    with open(filename, encoding='utf-8') as f:
         for line in f:
             [key, data] = line.split('->')
             # TODO for now, convert both to lower. Someday we can maybe add
@@ -767,7 +766,7 @@ def parse_file(filename, colors, summary, misspellings, exclude_lines,
                 print("%sFIXED:%s %s"
                       % (colors.FWORD, colors.DISABLE, filename),
                       file=sys.stderr)
-            with codecs.open(filename, 'w', encoding=encoding) as f:
+            with open(filename, 'w', encoding=encoding, newline='') as f:
                 f.writelines(lines)
     return bad_count