DOC, BLD: make the python docs build failures print a nicer message (#50356)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/50330
- Encapsulate the `make html` call and capture the stdout/stderr with a `tee` command
- If the buld fails, print out the `WARNING:` lines of the build log and finish up with a message
I tried it out on my branch, but did not write a test.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/50356
Reviewed By: ezyang
Differential Revision: D26101762
Pulled By: brianjo
fbshipit-source-id: ba2b704d3244ef5139ca9026c5250537bf45734f
