docs: def check_schema(self):
          """Check the schema exists and matches configuration"""
          if self.valid_schema:
              return
          config = self.config
          metadata = self.metadata()
          if 'current_version' not in metadata:
              raise GaugedSchemaError('Gauged schema not found, '
                                      'try a gauged.sync()')
          if metadata['current_version'] != Gauged.VERSION:
              msg = 'The schema is version %s while this Gauged is version %s. '
              msg += 'Try upgrading Gauged and/or running gauged_migrate.py'
              msg = msg % (metadata['current_version'], Gauged.VERSION)
              raise GaugedVersionMismatchError(msg)
          expected_block_size = '%s/%s' % (config.block_size, config.resolution)
          block_size = '%s/%s' % (metadata['block_size'], metadata['resolution'])
          if block_size != expected_block_size:
              msg = 'Expected %s and got %s' % (expected_block_size, block_size)
              warn(msg, GaugedBlockSizeMismatch)
          self.valid_schema = True