Make trust handle use ensure_async

[vidartf]

Fixes #372.

Blind edit via web, so not tested yet. I'll see if I can add a regression test as well.

[codecov-io]

Codecov Report

Merging #373 (ee6c909) into master (00a6e25) will increase coverage by 0.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #373      +/-   ##
==========================================
+ Coverage   69.29%   69.35%   +0.06%     
==========================================
  Files          56       56              
  Lines        6135     6135              
  Branches      804      804              
==========================================
+ Hits         4251     4255       +4     
+ Misses       1616     1612       -4     
  Partials      268      268              

Impacted Files	Coverage Δ
jupyter_server/services/contents/handlers.py	84.17% <100.00%> (+2.53%)	⬆️

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[kevin-bates]

These changes look good Vidar and are consistent with what the code was doing before the async/await sweep. Thanks for adding the test as well!

The current test snafus appear to be unrelated.

[Zsailer]

The current test snafus appear to be unrelated.

Yeah, oddly, culling kernels on any OS using PyPy seems to take an unpredictable/flaky amount of time (see this line).

I'll cut a patch release with these changes today.