docs: def init_app(self, app):
          """
          Find and configure the user database from specified file
          """
          app.config.setdefault('FLASK_AUTH_ALL', False)
          app.config.setdefault('FLASK_AUTH_REALM', 'Login Required')
          # Default set to bad file to trigger IOError
          app.config.setdefault('FLASK_HTPASSWD_PATH', '/^^^/^^^')
  
          # Load up user database
          try:
              self.load_users(app)
          except IOError:
              log.critical(
                  'No htpasswd file loaded, please set `FLASK_HTPASSWD`'
                  'or `FLASK_HTPASSWD_PATH` environment variable to a '
                  'valid apache htpasswd file.'
              )
  
          # Allow requiring auth for entire app, with pre request method
          @app.before_request
          def require_auth():  # pylint: disable=unused-variable
              """Pre request processing for enabling full app authentication."""
              if not current_app.config['FLASK_AUTH_ALL']:
                  return
              is_valid, user = self.authenticate()
              if not is_valid:
                  return self.auth_failed()
              g.user = user