docs: def load(self):
          """(Re)Load config file."""
          try:
              with open(self.config_file) as configfile:
                  self.config = yaml.load(configfile)
          except TypeError:
              # no config file (use environment variables)
              pass
          if self.config:
              self.prefix = self.config.get('config_prefix', None)
          if not self.prefix:
              if os.getenv(self.config_prefix):
                  self.prefix = os.getenv(self.config_prefix)
              else:
                  for path in [
                      os.path.join(self.basepath, self.default_file),
                      os.path.join(self.config_root, self.default_file)
                  ]:
                      if os.path.exists(path):
                          with open(path) as conf:
                              config = yaml.load(conf)
                              prefix = config.get(
                                  self.config_prefix.lower(), None
                              )
                              if prefix:
                                  self.prefix = prefix
                                  break