localized error message when inviting a user is missing the username

1. head over to {{User / Preferences / Actions / Edit Locale Setting}
2. choose French
3. create a user with mail alfred@nuxeo.com
4. head over to a workspace
5. click Manage / User invitations
6. type the alfred@nuxeo.com
7. submit the form

Notice the error message is not evaluated in French and displays

{0}

instead.

This is due to the property label.unicity.sameemail. It contains a single quote that should be escaped by a second single quote. Replacing it inside the jar validates this solution.

in OSGI-INF/l10n/messages_fr_FR.properties
and in i18n/messages_fr.properties