docs: function describeFailure(ex) {
    return ex.stack?        ['  ---'
                            ,'    type: ' + ex.name
                            ,'    message: >'
                            ,       pad(6, ex.message)
                            ,'    stack: | '
                            ,       pad(6, ex.stack)
                            ,'  ...'
                            ].join('\n')
    :      /* otherwise */  ['  ---'
                            ,'    message: >'
                            ,       pad(6, ex.toString())
                            ,'  ...'
                            ].join('\n')
  }