jupyter-run: avoid traceback for NoSuchKernel

[minrk]

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NoSuchKernel used to raise during KernelManager instantiation, but it is now delayed, so our except NoSuchKernel isn't catching the error when it's raised anymore.

Access kernel_spec to ensure it's raised where it will be caught.

Also removes a redundant warning log immediately before raising, which prevents complete handling of NoSuchError and produces unavoidable duplicate logs.

Test added for runapp, both regression for #993 and simple exercise for everything working correctly.

closes #993

[minrk]

need to investigate why the minimum version test doesn't see any output. Hard to compare, since the test jobs don't show what packages are installed, so I can't easily diff or reproduce the envs.

[blink1073]

The minimum tests use hatch --v run, you can add that to the standard tests to compare.