The transition of the SageCell online computer algebra system from using SageMath 2.8 to 2.9 and from Python 2 to Python 3 broke some Sagecell code that used to work previously. The table below lists such problems, together with workarounds (where known). For background information see the Python3-Switch-wiki-page.
If you encounter such a problem with previously working code, please try to isolate the problem in a small code snippet and report it here. No registration needed, just submit your code and the resulting error message.
Note: This page is only for handling recent errors reproducable on https://sagecell.sagemath.org, either directly or embedded into other web pages. Other installations of SageCell may show a different behaviour.
Please, use the SageCell Google group for the discussion of any other problem!
You can use the thread "Repairing Broken Code" in the aformentioned Google group for the occasional submission of particular solutions. If you are available for regularly submitting solutions, ask in that group for a private link for directly editing the table below.