code: def build_config(config_file=get_system_config_directory()):
      
      config = Config(config_file, allow_no_value=True)
      application_versions = find_applications_on_system()
  
      # Add found versions to config if they don't exist. Versions found
      # in the config file takes precedence over versions found in PATH.
      for item in application_versions.iteritems():
          if not config.has_option(Config.EXECUTABLES, item[0]):
              config.set(Config.EXECUTABLES, item[0], item[1])
      return config
docs: Construct the config object from necessary elements.