JSON output file not JSON conformant

The JSON output file is not JSON conformant in two aspects:

1. Single quotes (') are used instead of double quotes(")
2. Some words such as None, True or False are not wrapped in any quotes at all

This may affect some simpler JSON parsers, better JSON parsers can handle these minor errors just fine.


```
'error': None
#should be
"error": "None"
```