code: function (command, responseCallback) {
      if (command.passphrase === true) {
        cliUtil.getValueFromPrompt('private key passphrase', true,
          function (error, passphrase) {
            if (error) {
              provisionUtil.invokeCallback(error, responseCallback,
                command.verbosity)
            } else {
              command.passphrase = passphrase
              provisionUtil.invokeCallback(null, responseCallback)
            }
          }
        )
      } else {
        provisionUtil.invokeCallback(null, responseCallback)
      }
    }
docs: Process the private key passphrase from the supplied Commander-based
  command.
  @param {Command} command - Commander-based command which contains options
  to use in generating the CSR and private key.
  @param {(String|Boolean)} [command.passphrase] - If `true`, prompt from
  the command line for the private key passphrase to use and store the
  entered value back to the `command.passphrase` property.
  @param {Function} [responseCallback] - Function to invoke with the result
  from private key passphrase processing. The first parameter in the
  callback is an `Error` instance if the attempt to obtain the passphrase
  fails.