This is what babel-french urges, and canadien currently is broken.
acadien seems to be there for at least 15 years
# PolyglossiaOpts "variant=french"
Language canadien
GuiName "French (Canada)"
- BabelName canadien
+ BabelName acadian
# PolyglossiaName french
# PolyglossiaOpts "variant=canadien"
QuoteStyle french
- Fix loading order problem with rotfloat/rotating and graphicx (bug 11502).
+- Fix LaTeX error with Canadian French as second language. LyX now uses
+ the (recommended) babel option "acadian" rather than "canadien".
+
* USER INTERFACE