[pre-commit.ci] auto fixes from pre-commit.com hooks

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Author: pre-commit-ci[bot]

src/_pytest/pytester.py

@@ -1344,7 +1344,7 @@ def popen(
 
         You probably want to use :py:meth:`run` instead.
         """
-        env = kw.pop('env', None) or os.environ.copy()
+        env = kw.pop("env", None) or os.environ.copy()
         pythonpath = env.get("PYTHONPATH", "")
 
         paths_to_add = [os.getcwd()]