Provide more information for socket errors

[ricellis]

It would be helpful to provide additional error information in the message Nano outputs for socket or connection errors.

Expected Behavior

Suggest including, for example, reading the error .code and .description and adding it to the message to provide some more useful diagnostics.

{
  code: 'ECONNRESET',
  description: 'socket hang up'
}

err.message -> error happened in your connection ECONNRESET socket hang up

Current Behavior

Currently for a socket/connection error only the err.message is set to error happened in your connection.

err.message -> error happened in your connection

Possible Solution

Could build up the error message to include .code and .description if they are available e.g.

  if (err && err.code) {
    err.message = `${err.message} ${err.code}`;
  }
  if (err && err.description) {
    err.message = `${err.message} ${err.description}`;
  }

Steps to Reproduce (for bugs)

1. Could use nock replyWithError to reproduce e.g.

nock.get(...).replyWithError({'description': 'socket hang up', 'code': 'ECONNRESET'});

Context

Made it hard to debug some connection issues without adding additional output statements to see the underlying cause of the error. Similarly to #54 where the whole error object has been output because the message error happened in your connection is insufficient to identify the issue.

Your Environment

• Version used:

6.4.0

• Browser Name and version:

Node.js 8.2.0

• Operating System and version (desktop or mobile):

macOS 10.12.6

• Link to your project:

https://github.com/cloudant/nodejs-cloudant