Jormun&Kraken: add recoverable error

add a recoverable_exception for error on query.

when thrown kraken returns a internal_error but can continue serving other requests

for the current bug on service extention we'll get:
{

    "error": {
        "id": "internal_error",
        "message": "impossible to rebuild the public transport path"
    },
    "exceptions": [ ],
    "notes": [ ]

}