mix_stderr parameter was removed from click 8.2.0 (#4577)

tests/test_black.py

@@ -14,6 +14,7 @@
 from concurrent.futures import ThreadPoolExecutor
 from contextlib import contextmanager, redirect_stderr
 from dataclasses import fields, replace
+from importlib.metadata import version as imp_version
 from io import BytesIO
 from pathlib import Path, WindowsPath
 from platform import system
@@ -25,6 +26,7 @@
 import pytest
 from click import unstyle
 from click.testing import CliRunner
+from packaging.version import Version
 from pathspec import PathSpec
 
 import black
@@ -114,7 +116,10 @@ class BlackRunner(CliRunner):
     """Make sure STDOUT and STDERR are kept separate when testing Black via its CLI."""
 
     def __init__(self) -> None:
-        super().__init__(mix_stderr=False)
+        if Version(imp_version("click")) >= Version("8.2.0"):
+            super().__init__()
+        else:
+            super().__init__(mix_stderr=False)
 
 
 def invokeBlack(