code: def lookup(self, section, name):
          
          value = os.environ.get('AMAAS_{}'.format(name.upper()))
          if value:
              return value
  
          try:
              value = self.file_config.get(section, name)
          except ConfigParserError:
              pass
          else:
              if value:
                  return value
  
          raise MissingConfigurationError(section, name)
docs: Lookup config value.