fix tornado related warnings by replacing pytest-tornado with a simple coroutine runner

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (8028420) 92.32% compared to head (bf80673) 92.32%.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #810 +/- ## ======================================= Coverage 92.32% 92.32% ======================================= Files 27 27 Lines 1811 1811 Branches 338 338 ======================================= Hits 1672 1672 Misses 92 92 Partials 47 47 ```

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