[nuclearcat]

As reported in discord, often error messages are not really helpful, so we need to improve them.

    kci-dev --instance dev maestro results --nodeid 69a01f7ebdc4039366c2729b
            "error_code": "submit_error",
            "error_msg": "400 Client Error: Bad Request for url: https://lava.XXX.com/api/v0.2/jobs/?format=json&limit=256",

We will try to decode now body as well, if it is json - try to extract variable, if not - all content, but truncate to 512 chars, so mongodb and other storages wont explode from lengthy messages.