Emit a warning on invalid syntax in files or in doc code-blocks

[Zac-HD]

echo 1/ > t.py && shed t.py reports an internal error, because the file contents are not syntactically valid Python. We should just emit a warning in this case. CC @rsokl 😉

[Zac-HD]

As of shed == 0.4.1, this is no longer an error - but we silently skip such broken bits of code, and I'd prefer to emit a warning or print to stderr. Challenge: thread through a location param to use in such a warning, and ideally make it warning when used in code - caught and printed to stderr when in the CLI.

[rsokl]

Sorry for not just opening an issue earlier! I can confirm that the internal errors I was getting on 0.3.10, e.g.

Internal error formatting 'README.md': Cannot parse: 1:0: >>> from hydra_zen import builds

were indeed related to me using a python code block where I should be using a pycon one. I can also confirm that 0.4.1 runs without issue on the same project!

[Zac-HD]

Fixed by c2414fe: from version 0.4.2, shed reports

$ shed hydra-zen/README.md
Could not parse ```python markdown block in file 'hydra-zen/README.md'
    Perhaps you should use a 'pycon' block instead?
Could not parse ```python markdown block in file 'hydra-zen/README.md'
    Perhaps you should use a 'pycon' block instead?

and successfully formats the actually-python code blocks in the same pass 🚀