1 - No message if no user or no group have been selected : 

To reproduce : 

1a - Fill only a message (set user list and group list empty)

2b - Click on Send button => Pop-up is closed KO

=> A message should be displayed (telling that no user nor group have been selected) and pop-up should not been closed. 

2 - Message is a mandatory field, consequently "Vous pouvez ajouter un message ..." is incorrect. 

It should be : "Ajoutez un message personnalisé de 200 caractères maximum"

=> To be done also in english :  "Add a personalized message of 200 maximum characters"

3 - Tool tip is not homogeneous (de la page, des pages) : 

Update the first part "Ce bouton ... de la publication des pages". 

=> In english : 

Update the first part : "This button ... that the pages are published online."