Fix check_untyped_defs errors in capture

src/_pytest/capture.py

@@ -12,6 +12,7 @@ from tempfile import TemporaryFile
 
 import pytest
 from _pytest.compat import CaptureIO
+from _pytest.fixtures import FixtureRequest
 
 patchsysdict = {0: "stdin", 1: "stdout", 2: "stderr"}
 
@@ -241,13 +242,12 @@ class CaptureManager:
 capture_fixtures = {"capfd", "capfdbinary", "capsys", "capsysbinary"}
 
 
-def _ensure_only_one_capture_fixture(request, name):
-    fixtures = set(request.fixturenames) & capture_fixtures - {name}
+def _ensure_only_one_capture_fixture(request: FixtureRequest, name):
+    fixtures = sorted(set(request.fixturenames) & capture_fixtures - {name})
     if fixtures:
-        fixtures = sorted(fixtures)
-        fixtures = fixtures[0] if len(fixtures) == 1 else fixtures
+        arg = fixtures[0] if len(fixtures) == 1 else fixtures
         raise request.raiseerror(
-            "cannot use {} and {} at the same time".format(fixtures, name)
+            "cannot use {} and {} at the same time".format(arg, name)
         )