* The current Tempest auth providers check for a very specific
timestamp format for the "expires" field of token responses.
If the Identity provider sends a response with a valid timestamp
that does not exactly match this format, test execution is halted.
Since the auth provider is client code, any specific functional
checks would be better represented as a test. The client is
primarily concerned with if the value can be parsed successfully.
The current guidance from the API working group is that any
valid ISO 8601 compliant timestamp should be sufficient.
https://github.com/openstack/api-wg/blob/master/guidelines/time.rst
Change-Id: I7b8e9435b5b94a6237f300366952f6d2f6414e42
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