code: def test_load_from_missing_file(self):
      with self.assertRaisesRegex(
          exceptions.ConfigurationError,
          "Config file 'missing_file.yml' does not exist.",
      ):
          base.load_config(config_file="missing_file.yml")
  
imports: import os
  import unittest
  from mkdocs import exceptions
  from mkdocs.config import base
  from mkdocs.config import config_options
  from mkdocs.config import defaults
  from mkdocs.config.base import ValidationError
  from mkdocs.tests.base import change_dir, tempdir
label_desc: Use image node_id 7 for calling the ConfigBaseTests obj's underlying member method code with example usage: obj.test_load_from_missing_file() without return types