5.0: please run_constrained nbconvert

[bollwyvl]

Solution to issue cannot be found in the documentation.

• I checked the documentation.

Issue

Hooray bleach 5.0!

Boo for unpinned downstreams, a la jupyter/nbconvert#1754

I guess if possible, it would be lovely to preemtively have:

run_constrained:
  - nbconvert <6.5

But i don't know how quickly we'd be able to handle the transition, if we were able to support both.

Installed packages

ncbonvert <=6.4.3
bleach 5.0.0

Environment info

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