*Note*: Before submitting this pull request, please review our [contributing
guidelines](https://docs.celeryq.dev/en/main/contributing.html).

## Description

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Fixes #8499.  The `isoparse` from dateutil is more correct about what it supports, handling the 'Z' timezone as well, which earlier versions of Python didn't support.  

I'm not 100% sure where the user is providing the eta as a string to, since apply_async notes it to be a datetime.  If someone can point me to that and a simple test case, I'll add some additional date strings there to catch this in the future.

Replaces datetime.fromisoformat with the more lenient dateutil parser. *Note*: Before submitting this pull request, please review our [contributing
guidelines](https://docs.celeryq.dev/en/main/contributing.html).

## Description

<!-- Please describe your pull request.

NOTE: All patches should be made against main, not a maintenance branch like
3.1, 2.5, etc.  That is unless the bug is already fixed in main, but not in
that version series.

If it fixes a bug or resolves a feature request,
be sure to link to that issue via (Fixes #4412) for example.
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Fixes #8499.  The `isoparse` from dateutil is more correct about what it supports, handling the 'Z' timezone as well, which earlier versions of Python didn't support.  

I'm not 100% sure where the user is providing the eta as a string to, since apply_async notes it to be a datetime.  If someone can point me to that and a simple test case, I'll add some additional date strings there to catch this in the future.

=====================================================
 ``celery.bin.logtool``
=====================================================

.. contents::
    :local:
.. currentmodule:: celery.bin.logtool

.. automodule:: celery.bin.logtool
    :members:
    :undoc-members:

=====================================================
 ``celery.bin.logtool``
=====================================================

.. contents::
    :local:
.. currentmodule:: celery.bin.logtool

.. automodule:: celery.bin.logtool
    :members:
    :undoc-members:
