Scheduler only valid when a broker exists

[alanpaxton]

Description:

Scheduler functions retrieve a scheduler from their context's broker, which does not exist unless they are constructed with a module context. I don't think they have ever been tested.

Reference:

Tests:

Expecting tests from a forthcoming PR from Lauretta to validate this. I have tested with a variation of the test, but I don't want to conflict.

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[codacy-production]

Not up to standards ⛔

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