OSError when the file system is not available

[williballenthin]

Textual (specifically App and DOMNode) assumes that the file containing source code for Widget classes is available and raises an OSError when this is not the case. This information is used to render the location of CSS styles.

I'm trying to get a Textual app running in an environment in which getpath doesn't work (Pyodide) because there's no file system in WebAssembly. Obviously, this is a pretty extreme environment, but I think the bug remains reasonable to address.

The calls to getfile are already wrapped in a try/except for TypeError with fallback behavior, so I propose that OSError be handled here, too. I can provide a standalone test case, though it's a little involved, so I'd rather just open a PR shortly, if you'll consider it.

[github-actions]

We found the following entry in the FAQ which you may find helpful:

• How do I center a widget in a screen?

Feel free to close this issue if you found an answer in the FAQ. Otherwise, please give us a little time to review.

This is an automated reply, generated by FAQtory

[github-actions]

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