Guide to build docs locally does not mention PyMC must be installed in a ipykernel named Python3

[ricardoV94]

Description

https://www.pymc.io/projects/docs/en/stable/contributing/build_docs.html

CC @OriolAbril

[ricardoV94]

Adding this variable in conf.py fixes it:

[twiecki]

@ricardoV94 Want to do a PR? :P

[OriolAbril]

I think it's not as much that a python3 kernel is available, more than no kernel is registered with that name and available from other envs. IIUC, having only a kernel named pymc in the local env for example and no other kernels available, the local one is used. But if a different env exposes a python3 kernel then the python3 will be used.

The variable in conf.py can be used as a workaround to circumvent the situation I mentioned above, but it should not be commited