= Fix the imports of shared exceptions =
Shared tempest exceptions (like TimeoutException) are defined
in and exported by tempest.lib, so use them correctly.
= Directly define the exceptions used by this tempest plugin =
While those exceptions have been defined in tempest.lib through
I62e0ba556b884c94f6e8796a2e6f6d8083277fa4,
they really belongs to this plugin only, so define them here.
Other tempest plugins followed the same pattern.
Moreover, the current import would need to be fixed anyway,
because it should import the exceptions from tempest.lib.exceptions
instead of tempest.exceptions.
Closes-Bug: #1858417
Closes-Bug: #1889537
Change-Id: Ie54c2a1dc25b647a0f0d10bcad6ba62023986741
f1432e10e1