title: ValueError. save() prohibited to prevent data loss due to unsaved related object 'filiere'
body: <p>When validating my form I get an error that says:
  valueError, save () prohibited to prevent data. loss die to unsaved related object 'filiere'
  Here is an excerpt from the code:</p>
  
  <pre><code>   fil = Filiere(nom_filiere=filiere)
     niv = Niveau.objects.create(niveau=niveau, filiere=fil)
  </code></pre>
  
  <p>I don't want to create or save fil(fil.save()) because "filiere" already exists in the database, I just want make the link between "niveau" and "filiere"</p>