Encoding error on Windows when generating report

[dalestee]

We can reproduce a Windows encoding issue when generating the HTML report.

The export code writes the file using the platform default encoding, which raises:

UnicodeEncodeError: 'charmap' codec can't encode character ...

A minimal fix is to write the HTML explicitly as UTF-8 in generation.py:

with open(output_file, "w", encoding="utf-8") as file:
    file.write(body)

[immu4989]

Confirmed on master (ba3e77b):

The offending call is at shapash/report/generation.py:93 inside export_and_save_report():

(body, resources) = exporter.from_filename(filename=os.path.join(working_dir, "base_report.ipynb"))

with open(output_file, "w") as file:
    file.write(body)

body is the HTML export from nbconvert.HTMLExporter, so it can contain arbitrary Unicode (feature names with accents, user-supplied text in additional data, dataset string values, etc.). open(..., "w") without an explicit encoding= falls back to locale.getpreferredencoding(False), which on Windows is cp1252 — hence the UnicodeEncodeError: 'charmap' codec can't encode character ... reported.

Grepped the rest of shapash/: every other write-side open() call is in binary mode (utils/io.py:41 writes pickles), and the read-side ones touch ASCII-only bundled JSON. So this is the only site that needs the fix.

Happy to send a PR that:

1. Applies the one line fix exactly as you proposed (encoding="utf-8").
2. Adds a small regression test in tests/integration_tests/test_report_generation.py that monkeypatches locale.getpreferredencoding to 'cp1252' and verifies the export still completes when body contains non-ASCII characters — so this can't silently regress on Linux/macOS CI runners.

Let me know if that test strategy looks reasonable to you — happy to drop the test if you'd rather keep the change strictly minimal, or to widen it to also cover the read-side encoding in utils/io.py:93 (with open(path) as f:) if you want one PR to cover all report-related encoding ambiguity.
My preference would be to keep the scope narrow to match the bug.