add constraint and change error form for missing field key

ldvspec/lofardata/forms.py

+from django.core.exceptions import ValidationError
+
 from .models import WorkSpecification, DataProductFilter
 
 from django.forms import ModelForm
@@ -20,6 +22,9 @@ class WorkSpecificationForm(ModelForm):
     def clean(self):
         self.cleaned_data = super().clean()
         self.cleaned_data["filters"] = self._extract_filters()
+        if not 'obs_id' in self.cleaned_data["filters"]:
+            raise ValidationError(["You have forgotten about the 'obs_id'"])
+
         return self.cleaned_data
 
     class Meta:

ldvspec/lofardata/templates/lofardata/workspecification/create_update.html

@@ -204,7 +204,11 @@
                             The input is invalid:
                             {% for field, errors in form.errors.items %}
                                 {% for error in errors %}
-                                    <li class="text text--red text--faded">{{ field }}: {{ error }}</li>
+                                    {% if field == '__all__' %}
+                                        <li class="text text--red text--faded">{{ error }}</li>
+                                    {% else %}
+                                        <li class="text text--red text--faded">{{ field }}: {{ error }}</li>
+                                    {% endif %}
                                 {% endfor %}
                             {% endfor %}
                         </div>