I recently encountered this problem and stumbled upon this question.
I resolved it with a much easier way.
Method One
You can either remove the dataType: 'json' property from the object literal…
Method Two
Or you can do what @Sagiv was saying by returning your data as Json.
The reason why this parsererror message occurs is that when you simply return a string or another value, it is not really Json, so the parser fails when parsing it.
So if you remove the dataType: json property, it will not try to parse it as Json.
With the other method if you make sure to return your data as Json, the parser will know how to handle it properly.