def call!(env)
      status, headers, body = @app.call(env)
      if error = env['deas.error']
        error_body = Body.new(error)

        headers['Content-Length'] = error_body.size.to_s
        headers['Content-Type']   = error_body.mime_type.to_s
        body = [error_body.content]
      end
      [status, headers, body]
    end
def call!(env)
      status, headers, body = @app.call(env)
      if error = env['deas.error']
        error_body = Body.new(error)

        headers['Content-Length'] = error_body.size.to_s
        headers['Content-Type']   = error_body.mime_type.to_s
        body = [error_body.content]
      end
      [status, headers, body]
    end
The real Rack call interface.