Fix for the unwanted error log due to promotion from `float` to `Decimal` in Weboob fake bank module.
Fix for the unwanted error log due to promotion from `float` to
`Decimal` in Weboob fake bank module.

Closes #661.

bnjbvr/kresus,ZeHiro/kresus,bnjbvr/kresus,ZeHiro/kresus,bnjbvr/kresus,ZeHiro/kresus,ZeHiro/kresus,bnjbvr/kresus