Use PytestWarning and tweak the message

Author: nicoddemus

src/_pytest/fixtures.py

@@ -71,6 +71,7 @@
 from _pytest.scope import HIGH_SCOPES
 from _pytest.scope import Scope
 from _pytest.warning_types import PytestRemovedIn9Warning
+from _pytest.warning_types import PytestWarning
 
 
 if sys.version_info < (3, 11):
@@ -1564,7 +1565,9 @@ def _getusefixturesnames(self, node: nodes.Item) -> Iterator[str]:
         """Return the names of usefixtures fixtures applicable to node."""
         for marker_node, mark in node.iter_markers_with_node(name="usefixtures"):
             if not mark.args:
-                marker_node.warn(Warning("usefixtures() is empty, so it has no effect"))
+                marker_node.warn(
+                    PytestWarning("usefixtures() without arguments has no effect")
+                )
             yield from mark.args
 
     def getfixtureclosure(

testing/python/fixtures.py

@@ -1436,6 +1436,7 @@ def test_two(self):
         reprec.assertoutcome(passed=2)
 
     def test_empty_usefixtures_marker(self, pytester: Pytester) -> None:
+        """Empty usefixtures() marker issues a warning (#12439)."""
         pytester.makepyfile(
             """
             import pytest
@@ -1447,7 +1448,7 @@ def test_one():
         )
         result = pytester.runpytest()
         result.stdout.fnmatch_lines(
-            "*Warning: usefixtures() is empty, so it has no effect"
+            "*PytestWarning: usefixtures() without arguments has no effect"
         )
 
     def test_usefixtures_ini(self, pytester: Pytester) -> None: