parse_rfc3339 calling .groups() on None

[NilsJPWerner]

What happened (please include outputs or screenshots):

When the KubernetesPodOperator in airflow runs it outputs this log without breaking.
{kube_config.py:520} ERROR - 'NoneType' object has no attribute 'groups'

I have traced it back to the parse_rfc3339 function that is not guarding against search returning None.
https://github.com/kubernetes-client/python/blob/master/kubernetes/base/config/kube_config.py#L515-L520
https://github.com/kubernetes-client/python/blob/master/kubernetes/base/config/dateutil.py#L50-L77

What you expected to happen:
parse_rfc3339 should guard against this better and/or have a better error message that shows the string the regex is running on.

[roycaihw]

/help
/good-first-issue

[k8s-ci-robot]

@roycaihw:
This request has been marked as suitable for new contributors.

Guidelines

Please ensure that the issue body includes answers to the following questions:

• Why are we solving this issue?
• To address this issue, are there any code changes? If there are code changes, what needs to be done in the code and what places can the assignee treat as reference points?
• How can the assignee reach out to you for help?

For more details on the requirements of such an issue, please see here and ensure that they are met.

If this request no longer meets these requirements, the label can be removed
by commenting with the /remove-good-first-issue command.

In response to this:

/help
/good-first-issue

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.