raise PapermillExecutionError when CellExecutionError is raised without cell error output

[mbektas]

When notebooks with cell / line magics are executed and if the magic command fails, papermill doesn't throw any exception and returns exit code 0. This is because papermill relies on cell error output to raise PapermillExecutionError.

When magic commands fail, CellExecutionError is still thrown and recorded as cell metadata, and notebook execution stops. However, since these errors don't produce any cell error output, no exception is raised.

Changes in this PR check cell metadata for exceptions recorded by papermill (due to CellExecutionError) in addition to cell error outputs and raise PapermillExecutionError in those cases.

fixes #501, #381

[ibdafna]

@MSeal apologies for the direct ping. Let us know if there's anything we can do to get this one over the line. Many thanks

[MSeal]

There's a subtle case where non-blocking exceptions are raised are intended to not fail cell execution, but it's a much smaller edge case than the exception with no output this PR is fixing (plus I believe other interfaces are leaning into the same tradeoff). Thanks for putting this together!

[mbektas]

thanks for the review @MSeal! I ran unit tests locally and they were passing. I will look into failing CI checks.

[MSeal]

@mbektas No problem. I should be checking these more regularly.

The current test failure is unrelated to this PR. If you have a few minutes to add a test for the new exception detection it'd be appreciated. Independently I will go fix the unrelated test if you don't patch it yourself and get this merged when I get back from this work trip.

[codecov]

Codecov Report

Merging #786 (5d69044) into main (cb2eb37) will decrease coverage by 0.26%.
Report is 4 commits behind head on main.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #786      +/-   ##
==========================================
- Coverage   91.54%   91.29%   -0.26%     
==========================================
  Files          17       17              
  Lines        1621     1631      +10     
==========================================
+ Hits         1484     1489       +5     
- Misses        137      142       +5     

[mbektas]

The current test failure is unrelated to this PR.

I just fixed the failing test, it was due to a deprecated pytest feature. I will also be adding test(s) for the magic command error handling.

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[mbektas]

@MSeal I added a unit test for magic command failures as well. Looks like workflow needs your approval to run again.