Does not set status codes on operation errors

[larkee]

Raised in a Cloud Spanner issue, the returned GoogleAPICallError has a code and grpc_status_code of None.

The issue seems to be at:
https://github.com/googleapis/python-api-core/blob/master/google/api_core/operation.py#L135

The GoogleAPICallError constructor does not set the code from the errors argument so the error code contained within it is being lost.

[skuruppu]

CC @odeke-em and @skuruppu

[busunkim96]

I can get the code into the Exception by tweaking the bit of code @larkee highlighted to use from_grpc_status

            elif self._operation.HasField("error"):
                exception = exceptions.from_grpc_status(
                    status_code=self._operation.error.code,
                    message=self._operation.error.message,
                    errors=(self._operation.error,),
                    response=self._operation,
                )

                self.set_exception(exception)

Even after that change I seemed to always get GoogleAPICallError instead of one of the more specific exception types.

python-api-core/google/api_core/exceptions.py

Lines 188 to 193 in 339b07d

	class FailedPrecondition(BadRequest):
	"""Exception mapping a :attr:`grpc.StatusCode.FAILED_PRECONDITION`
	error."""
	grpc_status_code = grpc.StatusCode.FAILED_PRECONDITION if grpc is not None else None

The root cause seems to be that the dict that maps status codes to exception types expects grpc.StatusCode (not ints).

>>> from google.api_core import exceptions
>>> exceptions._GRPC_CODE_TO_EXCEPTION
{<StatusCode.INVALID_ARGUMENT: (3, 'invalid argument')>: <class 'google.api_core.exceptions.InvalidArgument'>, <StatusCode.FAILED_PRECONDITION: (9, 'failed precondition')>: <class 'google.api_core.exceptions.FailedPrecondition'>, <StatusCode.OUT_OF_RANGE: (11, 'out of range')>: <class 'google.api_core.exceptions.OutOfRange'>, <StatusCode.UNAUTHENTICATED: (16, 'unauthenticated')>: <class 'google.api_core.exceptions.Unauthenticated'>, <StatusCode.PERMISSION_DENIED: (7, 'permission denied')>: <class 'google.api_core.exceptions.PermissionDenied'>, <StatusCode.NOT_FOUND: (5, 'not found')>: <class 'google.api_core.exceptions.NotFound'>, <StatusCode.ALREADY_EXISTS: (6, 'already exists')>: <class 'google.api_core.exceptions.AlreadyExists'>, <StatusCode.ABORTED: (10, 'aborted')>: <class 'google.api_core.exceptions.Aborted'>, <StatusCode.RESOURCE_EXHAUSTED: (8, 'resource exhausted')>: <class 'google.api_core.exceptions.ResourceExhausted'>, <StatusCode.CANCELLED: (1, 'cancelled')>: <class 'google.api_core.exceptions.Cancelled'>, <StatusCode.INTERNAL: (13, 'internal')>: <class 'google.api_core.exceptions.InternalServerError'>, <StatusCode.UNKNOWN: (2, 'unknown')>: <class 'google.api_core.exceptions.Unknown'>, <StatusCode.DATA_LOSS: (15, 'data loss')>: <class 'google.api_core.exceptions.DataLoss'>, <StatusCode.UNIMPLEMENTED: (12, 'unimplemented')>: <class 'google.api_core.exceptions.MethodNotImplemented'>, <StatusCode.UNAVAILABLE: (14, 'unavailable')>: <class 'google.api_core.exceptions.ServiceUnavailable'>, <StatusCode.DEADLINE_EXCEEDED: (4, 'deadline exceeded')>: <class 'google.api_core.exceptions.DeadlineExceeded'>}

It wasn't clear to me how to get the enum from an int, so I opened https://groups.google.com/forum/#!topic/grpc-io/EdIXjMEaOyw.