Refactor handling of non-top-level pytest_plugins handling

Decided to move the 'if' logic together with the error message, as this leaves
the _importconftest method cleaner.

Author: nicoddemus

src/_pytest/config/__init__.py

@@ -286,19 +286,6 @@ def _prepareconfig(
         raise
 
 
-def _fail_on_non_top_pytest_plugins(conftestpath, confcutdir):
-    msg = (
-        "Defining 'pytest_plugins' in a non-top-level conftest is no longer supported:\n"
-        "It affects the entire test suite instead of just below the conftest as expected.\n"
-        "  {}\n"
-        "Please move it to a top level conftest file at the rootdir:\n"
-        "  {}\n"
-        "For more information, visit:\n"
-        "  https://docs.pytest.org/en/latest/deprecations.html#pytest-plugins-in-non-top-level-conftest-files"
-    )
-    fail(msg.format(conftestpath, confcutdir), pytrace=False)
-
-
 class PytestPluginManager(PluginManager):
     """
     Overwrites :py:class:`pluggy.PluginManager <pluggy.PluginManager>` to add pytest-specific
@@ -527,15 +514,11 @@ def _importconftest(self, conftestpath):
 
         try:
             mod = conftestpath.pyimport()
-            if (
-                hasattr(mod, "pytest_plugins")
-                and self._configured
-                and not self._using_pyargs
-            ):
-                _fail_on_non_top_pytest_plugins(conftestpath, self._confcutdir)
         except Exception as e:
             raise ConftestImportFailure(conftestpath, sys.exc_info()) from e
 
+        self._check_non_top_pytest_plugins(mod, conftestpath)
+
         self._conftest_plugins.add(mod)
         self._conftestpath2mod[key] = mod
         dirpath = conftestpath.dirpath()
@@ -548,6 +531,23 @@ def _importconftest(self, conftestpath):
         self.consider_conftest(mod)
         return mod
 
+    def _check_non_top_pytest_plugins(self, mod, conftestpath):
+        if (
+            hasattr(mod, "pytest_plugins")
+            and self._configured
+            and not self._using_pyargs
+        ):
+            msg = (
+                "Defining 'pytest_plugins' in a non-top-level conftest is no longer supported:\n"
+                "It affects the entire test suite instead of just below the conftest as expected.\n"
+                "  {}\n"
+                "Please move it to a top level conftest file at the rootdir:\n"
+                "  {}\n"
+                "For more information, visit:\n"
+                "  https://docs.pytest.org/en/latest/deprecations.html#pytest-plugins-in-non-top-level-conftest-files"
+            )
+            fail(msg.format(conftestpath, self._confcutdir), pytrace=False)
+
     #
     # API for bootstrapping plugin loading
     #