allow pre_save_hook to cancel save with HTTPError

[minrk]

currently, all errors in pre_save_hook are caught and logged, making it impossible for pre_save_hook to be used for validation / quota enforcement / etc.

By allowing HTTPErrors to raise, save will be cancelled and the hook's error message will be shown to the user in a dialog.

For example:

from tornado.web import HTTPError

def fail_save_forbidden(model, path, **kw):
    if "forbidden" in path.split("/"):
        raise HTTPError(400, "Can't save forbidden files!")

c.ContentsManager.pre_save_hook = fail_save_forbidden

Brought up on the forum

[codecov-io]

Codecov Report

Merging #456 (40f653d) into master (bf00ad0) will increase coverage by 0.17%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #456      +/-   ##
==========================================
+ Coverage   77.50%   77.68%   +0.17%     
==========================================
  Files         105      106       +1     
  Lines        8936     9106     +170     
  Branches      956      972      +16     
==========================================
+ Hits         6926     7074     +148     
- Misses       1673     1680       +7     
- Partials      337      352      +15     

Impacted Files	Coverage Δ
jupyter_server/services/contents/manager.py	87.79% <0.00%> (-0.53%)	⬇️
jupyter_server/transutils.py	72.72% <0.00%> (-27.28%)	⬇️
jupyter_server/terminal/handlers.py	76.00% <0.00%> (-8.22%)	⬇️
jupyter_server/auth/security.py	76.00% <0.00%> (-2.69%)	⬇️
jupyter_server/services/contents/filemanager.py	66.09% <0.00%> (-0.86%)	⬇️
jupyter_server/terminal/__init__.py	79.16% <0.00%> (-0.84%)	⬇️
jupyter_server/utils.py	62.85% <0.00%> (-0.61%)	⬇️
jupyter_server/extension/application.py	72.36% <0.00%> (-0.09%)	⬇️
jupyter_server/tests/auth/test_security.py	100.00% <0.00%> (ø)
jupyter_server/tests/extension/conftest.py	100.00% <0.00%> (ø)
... and 8 more

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[blink1073]

Thanks!

[kevin-bates]

This will be useful - thanks.

We could probably use a test for this at some point.