Code review comment for lp:~andrewjbeach/juju-ci-tools/fix-wait-for-started

The Original Questions replied to: ==========================================
How should this mix with the existing error checks in Status? And the
existing Exception type ErroredUnit? Should some overhead StatusError class
be used?

Should the exception be raised within the check?

Are there any types of errors we want to give priority over others? If so how
do we keep them from getting shadowed by less important exceptions that just
happen to be found earlier?
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I added the exceptions mentioned as a first step. In addition to just being
new more particular exceptions StatusError and all of its children store a
recoverable value which marks if we think juju will recover from them.

We could store a time value if we want control over how often to re-try,
but I don't think we do.

All the classes are orderable within each other. After a sweep through the
Status any generated errors can be sorted to find the most important ones.
I tried encoding the sorting rules in code, but it was rather complex and
still required some manual ordering.