Move setup.cfg error message and tests to an appropriate location

Those are not really deprecated anymore and are part of the normal
code for config

src/_pytest/config/findpaths.py

@@ -20,8 +20,6 @@ def getcfg(args, config=None):
 
     note: config is optional and used only to issue warnings explicitly (#2891).
     """
-    from _pytest.deprecated import CFG_PYTEST_SECTION
-
     inibasenames = ["pytest.ini", "tox.ini", "setup.cfg"]
     args = [x for x in args if not str(x).startswith("-")]
     if not args:
@@ -97,6 +95,9 @@ def get_dirs_from_args(args):
     return [get_dir_from_path(path) for path in possible_paths if path.exists()]
 
 
+CFG_PYTEST_SECTION = "[pytest] section in {filename} files is no longer supported, change to [tool:pytest] instead."
+
+
 def determine_setup(inifile, args, rootdir_cmd_arg=None, config=None):
     dirs = get_dirs_from_args(args)
     if inifile:
@@ -107,8 +108,6 @@ def determine_setup(inifile, args, rootdir_cmd_arg=None, config=None):
             try:
                 inicfg = iniconfig[section]
                 if is_cfg_file and section == "pytest" and config is not None:
-                    from _pytest.deprecated import CFG_PYTEST_SECTION
-
                     fail(
                         CFG_PYTEST_SECTION.format(filename=str(inifile)), pytrace=False
                     )

src/_pytest/deprecated.py

@@ -33,8 +33,6 @@ FIXTURE_NAMED_REQUEST = PytestDeprecationWarning(
     "'request' is a reserved name for fixtures and will raise an error in future versions"
 )
 
-CFG_PYTEST_SECTION = "[pytest] section in {filename} files is no longer supported, change to [tool:pytest] instead."
-
 
 FUNCARGNAMES = PytestDeprecationWarning(
     "The `funcargnames` attribute was an alias for `fixturenames`, "

testing/deprecated_test.py

@@ -4,30 +4,6 @@ from _pytest import deprecated
 pytestmark = pytest.mark.pytester_example_path("deprecated")
 
 
-def test_pytest_setup_cfg_unsupported(testdir):
-    testdir.makefile(
-        ".cfg",
-        setup="""
-        [pytest]
-        addopts = --verbose
-    """,
-    )
-    with pytest.raises(pytest.fail.Exception):
-        testdir.runpytest()
-
-
-def test_pytest_custom_cfg_unsupported(testdir):
-    testdir.makefile(
-        ".cfg",
-        custom="""
-        [pytest]
-        addopts = --verbose
-    """,
-    )
-    with pytest.raises(pytest.fail.Exception):
-        testdir.runpytest("-c", "custom.cfg")
-
-
 @pytest.mark.filterwarnings("default")
 def test_resultlog_is_deprecated(testdir):
     result = testdir.runpytest("--help")

testing/test_config.py

@@ -1245,6 +1245,30 @@ def test_config_blocked_default_plugins(testdir, plugin):
         assert result.stdout.lines == [""]
 
 
+class TestSetupCfg:
+    def test_pytest_setup_cfg_unsupported(self, testdir):
+        testdir.makefile(
+            ".cfg",
+            setup="""
+            [pytest]
+            addopts = --verbose
+        """,
+        )
+        with pytest.raises(pytest.fail.Exception):
+            testdir.runpytest()
+
+    def test_pytest_custom_cfg_unsupported(self, testdir):
+        testdir.makefile(
+            ".cfg",
+            custom="""
+            [pytest]
+            addopts = --verbose
+        """,
+        )
+        with pytest.raises(pytest.fail.Exception):
+            testdir.runpytest("-c", "custom.cfg")
+
+
 class TestPytestPluginsVariable:
     def test_pytest_plugins_in_non_top_level_conftest_unsupported(self, testdir):
         testdir.makepyfile(