Add a regression test for #4746

This permits to introduce an example of configuration file with an error.

pylint/config/option_manager_mixin.py

@@ -271,6 +271,9 @@ def read_config_file(self, config_file=None, verbose=None):
 
         use_config_file = config_file and os.path.exists(config_file)
         if use_config_file:
+            mod_name = config_file
+            self.current_name = mod_name
+            self.set_current_module(mod_name)
             parser = self.cfgfile_parser
             if config_file.endswith(".toml"):
                 self._parse_toml(config_file, parser)

pylint/testutils/configuration_test.py

@@ -76,8 +76,8 @@ def get_expected_output(configuration_path: str) -> Tuple[int, str]:
 
     def get_relative_path(path: str) -> str:
         """Get the relative path we want without the user specific path"""
-        # Second [1:] is to remove the closing '/'
-        return "".join(path.split(USER_SPECIFIC_PATH)[1:][1:])
+        # [1:] is to remove the opening '/'
+        return path.split(USER_SPECIFIC_PATH)[1][1:]
 
     output = get_expected_or_default(configuration_path, suffix="out", default="")
     if output:
@@ -91,9 +91,8 @@ def get_relative_path(path: str) -> str:
     else:
         logging.info(".out file does not exists, so the expected exit code is 0")
         exit_code = 0
-    return exit_code, output.format(
-        abspath=configuration_path, relpath=get_relative_path(configuration_path)
-    )
+    relpath = get_relative_path(configuration_path)
+    return exit_code, output.format(abspath=configuration_path, relpath=relpath)
 
 
 def run_using_a_configuration_file(

tests/config/functional/toml/issue_4746/loaded_plugin_does_not_exists.out

@@ -0,0 +1,2 @@
+************* Module {abspath}
+{relpath}:1:0: E0013: Plugin 'pylint_websockets' is impossible to load, is it installed ? ('No module named 'pylint_websockets'') (bad-plugin-value)

tests/config/functional/toml/issue_4746/loaded_plugin_does_not_exists.result.json

@@ -0,0 +1,3 @@
+{
+  "load_plugins": ["pylint_websockets"]
+}

tests/config/functional/toml/issue_4746/loaded_plugin_does_not_exists.toml

@@ -0,0 +1,8 @@
+# The pylint_websockets plugin does not exist and therefore this toml is invalid
+[tool.poe.tasks]
+docs = {cmd = "sphinx-build docs build", help = "Build documentation"}
+
+[tool.pylint.MASTER]
+load-plugins = 'pylint_websockets'
+
+format = ["black", "isort"]