[PierreRaybaut]

Problem

guidata.configtools.get_translation calls gettext.translation(modname, modlocpath, fallback=True). fallback=True only handles missing catalogs: a .mo file that exists but is corrupted or unreadable raises OSError (bad magic number, file is corrupt, permission denied), struct.error (truncated file), ValueError (invalid UTF-8, invalid Plural-Forms) or LookupError (unknown charset).

As get_translation runs at import time (guidata.config, plotpy.config, sigima.config, datalab.config), a single corrupted catalog prevents every guidata-based application from starting.

Fix

• get_translation catches these errors, emits a RuntimeWarning naming the module, the locale directory and the underlying error, and returns the untranslated (English) callback (gettext.NullTranslations).
• The exception tuple is explicit (no bare Exception) so that programming errors are not hidden.
• gettext only caches successfully parsed catalogs, so no stale cache entry is left behind.

Tests

guidata/tests/unit/test_translations.py (Qt-free) builds GNU .mo catalogs in a temporary locale directory:

• 7 corrupted cases (bad magic number, empty file, truncated header, offsets past end of file, unknown charset, invalid UTF-8 translation, invalid Plural-Forms): RuntimeWarning + English fallback. All 7 fail without the fix.
• Valid catalog: translated, no warning.
• Missing catalog: English, no warning (unchanged behavior).

Validation:

• pytest (full guidata suite, Python 3.11): 251 passed, 2 skipped.
• ruff format / ruff check: clean.
• End-to-end smoke test: with a corrupted guidata fr catalog, guidata, plotpy.config, sigima.config and datalab.config all import; guidata falls back to English with the warning while DataLab's own catalog keeps working.

Release notes

Entry added to the Unreleased section of doc/release_notes/release_3.16.md (patch 3.16.x). To be cherry-picked into develop after merge.

Fixes #119