(semver-minor) define/export error constants

[techjeffharris]

defining and exporting constants to define various error messages
makes them easier and more reliable to compare and test

[techjeffharris]

The \n should probably not be in the constant.. I'll move it to the message concatenaed to it on line 79.

[jfromaniello]

I'd rather use the constant names you used as error codes?
And create an Error type that can accept code

[techjeffharris]

Something like

function PassportSocketIoError (code) {
  this.message = code
}

PassportSocketIoError.prototype = new Error();

var ERROR_NO_SESSION = 'No session found';

// during authorization
return auth.fail(data, new PassportSocketIoError(ERROR_NO_SESSION), false, accept);

...?

[techjeffharris]

I'd rather use the constant names you used as error codes?

Is this more to your liking?

var ERROR_USER_NOT_AUTHORIZED       = 'ERROR_USER_NOT_AUTHORIZED';
var ERROR_USER_NOT_FOUND            = 'ERROR_USER_NOT_FOUND';