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/dependencies/cuda.py b/mesonbuild/dependencies/cuda.py
index 20f6569..6d17b90 100644
--- a/mesonbuild/dependencies/cuda.py
+++ b/mesonbuild/dependencies/cuda.py
@@ -130,7 +130,7 @@ class CudaDependency(ExternalDependency):
     def _default_path_env_var(self):
         env_vars = ['CUDA_PATH'] if self._is_windows() else ['CUDA_PATH', 'CUDA_HOME', 'CUDA_ROOT']
         env_vars = [var for var in env_vars if var in os.environ]
-        user_defaults = set([os.environ[var] for var in env_vars])
+        user_defaults = {os.environ[var] for var in env_vars}
         if len(user_defaults) > 1:
             mlog.warning('Environment variables {} point to conflicting toolkit locations ({}). Toolkit selection might produce unexpected results.'.format(', '.join(env_vars), ', '.join(user_defaults)))
         return env_vars[0] if env_vars else None