A motivation letter must be a PDF/JPEG/PNG file (it didn't work)

apps/participation/forms.py

@@ -61,7 +61,7 @@ class ParticipationForm(forms.ModelForm):
 
 class MotivationLetterForm(forms.ModelForm):
     def clean_file(self):
-        if "file" in self.files:
+        if "motivation_letter" in self.files:
             file = self.files["motivation_letter"]
             if file.size > 2e6:
                 raise ValidationError(_("The uploaded file size must be under 2 Mo."))