Expectations fail callback function

[Casyfill]

It seems to be nice to be able to log out specific expectations that failed, when the Operator fails. I am not sure this should be internalized, so instead, perhaps it makes sense to set a callback function on fail?

I have something as naive as this in mind:

def generate_list_failed_expectations(r) -> str:
    """Note - only for validation results

    Input:
        r (reat_expectations.validation_operators.types.validation_operator_result.ValidationOperatorResult)
    Returns: str
    """
    from itertools import groupby

    lines = ["Validation with Great Expectations failed."]

    for batch, result in r["run_results"].items():
        lines.append(f"{batch}")
        failed = [
            r.expectation_config
            for r in result["validation_result"].results
            if not r.success
        ]
        for col, group_failed in groupby(failed, key=lambda k: k["kwargs"]["column"]):
            lines.append(f"  {col}")
            for test in group_failed:
                lines.append(f'    - {test["expectation_type"]}')
    raise AirflowException("\n".join(lines))