Hide warnings on fake inconsistencies when patching the nonexistent objects

[nolar]

Suppress the misleading warnings on inconsistencies when patching the object, which was deleted in/during the handling process.

Description

A snippet to reproduce the case:

import kopf
import pykube

class Kex(pykube.objects.NamespacedAPIObject):
    version = "zalando.org/v1"
    endpoint = "kopfexamples"
    kind = "KopfExample"

@kopf.on.create('zalando.org', 'v1', 'kopfexamples')
def create_fn(name, namespace, **_):
    api = pykube.HTTPClient(pykube.KubeConfig.from_env())
    obj = Kex.objects(api, namespace=namespace).get_by_name(name)
    obj.delete()
    return {'message': 'hello world'}  # will be the new status

Before the fix, it logged the following with the WARNING level:

[2020-10-05 19:54:40,612] kopf.objects         [INFO    ] [default/kopf-example-1] Handler 'create_fn' succeeded.
[2020-10-05 19:54:40,613] kopf.objects         [INFO    ] [default/kopf-example-1] Creation event is processed: 1 succeeded; 0 failed.
[2020-10-05 19:54:40,613] kopf.objects         [DEBUG   ] [default/kopf-example-1] Patching with: {'status': {'create_fn': {'message': 'hello world'}}, 'metadata': {'annotations': {'kopf.zalando.org/last-handled-configuration': '{"spec":{"duration":"1m","field":"value","items":["item1","item2"]},"metadata":{"labels":{"somelabel":"somevalue"},"annotations":{"someannotation":"somevalue"}}}\n'}}}
[2020-10-05 19:54:40,627] kopf.objects         [WARNING ] [default/kopf-example-1] Patching failed with inconsistencies: (('remove', ('status',), {'create_fn': {'message': 'hello world'}}, None), ('remove', ('metadata',), {'annotations': {'kopf.zalando.org/last-handled-configuration': '{"spec":{"duration":"1m","field":"value","items":["item1","item2"]},"metadata":{"labels":{"somelabel":"somevalue"},"annotations":{"someannotation":"somevalue"}}}\n'}}, None))
[2020-10-05 19:54:40,737] kopf.objects         [DEBUG   ] [default/kopf-example-1] Deleted, really deleted, and we are notified.

After the fix, the logs look like this, with only the DEBUG level messages:

[2020-10-05 19:50:56,919] kopf.objects         [INFO    ] [default/kopf-example-1] Handler 'create_fn' succeeded.
[2020-10-05 19:50:56,920] kopf.objects         [INFO    ] [default/kopf-example-1] Creation event is processed: 1 succeeded; 0 failed.
[2020-10-05 19:50:56,921] kopf.objects         [DEBUG   ] [default/kopf-example-1] Patching with: {'status': {'create_fn': {'message': 'hello world'}}, 'metadata': {'annotations': {'kopf.zalando.org/last-handled-configuration': '{"spec":{"duration":"1m","field":"value","items":["item1","item2"]},"metadata":{"labels":{"somelabel":"somevalue"},"annotations":{"someannotation":"somevalue"}}}\n'}}}
[2020-10-05 19:50:56,939] kopf.objects         [DEBUG   ] [default/kopf-example-1] Patching was skipped: the object does not exist anymore.
[2020-10-05 19:50:57,045] kopf.objects         [DEBUG   ] [default/kopf-example-1] Deleted, really deleted, and we are notified.

Inconsistency detection was introduced in #527 — to detect if CRDs are configured to lose the fields (e.g. due to "structural schemas" of K8s 1.16+). That case would be misbehaviour.

The object deletion in the handlers or during the handling process is, to some extent, an expected use-case. Instead of WARNING, which implies alerting and reaction, we now log only a DEBUG level message — to not leave the whole situation hidden (which might be needed for other cases of debugging).

Also, remove the frightening "failed" word, and replace it with "skipped" — to show that it was partially expected.