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

for more information, see https://pre-commit.ci

Author: pre-commit-ci[bot]

testing/conftest.py

@@ -89,7 +89,7 @@ def wd(tmp_path: Path) -> WorkDir:
 
 @pytest.fixture(scope="session")
 def hg_exe() -> str:
-    hg = shutil.which('hg')
+    hg = shutil.which("hg")
     if hg is None:
         pytest.skip("hg executable not found")
     return hg