various python neatness cleanups

All changes were created by running

"pyupgrade --py3-only --keep-percent-format"

and committing the results. I have not touched string formatting for
now.

- use set literals
- simplify .format() parameter naming
- remove __future__
- remove default "r" mode for open()
- use OSError rather than compatibility aliases
- remove stray parentheses in function(generator) scopes

1 files changed, 1 insertions, 1 deletions

diff --git a/mesonbuild/optinterpreter.py b/mesonbuild/optinterpreter.py
index dc8c3ce5c..60436911b 100644
--- a/mesonbuild/optinterpreter.py
+++ b/mesonbuild/optinterpreter.py
@@ -142,7 +142,7 @@ class OptionInterpreter:
 
     def process(self, option_file: str) -> None:
         try:
-            with open(option_file, 'r', encoding='utf8') as f:
+            with open(option_file, encoding='utf8') as f:
                 ast = mparser.Parser(f.read(), option_file).parse()
         except mesonlib.MesonException as me:
             me.file = option_file