Add test for ModuleNotFoundError fix

Refs #7938

tests/regrtest_data/importing_plugin/importing_plugin.py

@@ -0,0 +1,32 @@
+from importlib import import_module
+
+from pylint.checkers import BaseChecker
+from pylint.lint.pylinter import PyLinter
+
+
+class ImportingChecker(BaseChecker):
+    options = (
+        (
+            "settings-module",
+            {
+                "default": "settings",
+                "type": "string",
+                "metavar": "<settings module>"
+            },
+        ),
+    )
+
+    msgs = {
+        "E9999": (
+            "Importing checker error message",
+            "importing-checker-error",
+            "Importing checker error message",
+        ),
+    }
+
+    def open(self) -> None:
+        import_module(self.linter.config.settings_module)
+
+
+def register(linter: "PyLinter") -> None:
+    linter.register_checker(ImportingChecker(linter))

tests/test_self.py

@@ -869,6 +869,19 @@ def test_modify_sys_path() -> None:
                 modify_sys_path()
             assert sys.path == paths[1:]
 
+    @staticmethod
+    def test_plugin_that_imports_from_open() -> None:
+        """Test that a plugin that imports a source file from a checker open()
+        function (ala pylint_django) does not raise an exception."""
+        with _test_sys_path():
+            # Enable --load-plugins=importing_plugin
+            sys.path.append(join(HERE, "regrtest_data", "importing_plugin"))
+            with _test_cwd(join(HERE, "regrtest_data", "settings_project")):
+                Run(
+                    ["--load-plugins=importing_plugin", "models.py"],
+                    exit=False,
+                )
+
     @pytest.mark.parametrize(
         "args",
         [