Some improvements to findstat._submit

[user202729]

• for some reason the proper header is needed to open the HTML file on my machine.
• It's reported that webbrowser.open() doesn't work when called on a file path, rather an URI is needed (Allow Cython compilation to open a web browser containing the annotated HTML file #38946)

📝 Checklist

• The title is concise and informative.
• The description explains in detail what this PR is about.
• I have linked a relevant issue or discussion.
• I have created tests covering the changes.
• I have updated the documentation and checked the documentation preview. (not needed)

⌛ Dependencies

[github-actions]

Documentation preview for this PR (built with commit 4a82a39; changes) is ready! 🎉
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[mantepse]

I actually didn't realise that it was broken - I use it regularly. The main nuisance is that firefox doesn't access /tmp, so I also copy the created file manually...

[user202729]

webbrowser.open(file path) is platform dependent, https://docs.python.org/3/library/webbrowser.html#webbrowser.open .

The issue with /tmp/ is probably operating system/distribution dependent, see e.g. https://askubuntu.com/questions/1370653/snap-apps-dont-find-files-in-tmp .

Another approach might be to use data:html URL, but it isn't very clear that would be more platform independent than the current one. [edit: I just tried, webbrowser.open("data:text/html;base64,...") doesn't work. At least you can probably set $BROWSER to some custom script that copies the file somewhere else first]

[mantepse]

Looks OK - I cannot say much about it, though. There is no change visible to me on my system (Ubuntu 24.04).