[U] fix error when post office hour w/o login. returns json error

instead.

timer/forms.py

@@ -15,7 +15,7 @@ class OfficeHoursForm(forms.ModelForm):
 
   def full_clean(self):
     if not self.user.is_authenticated:
-      raise ValidationError('Invalid User.')
+      raise forms.ValidationError('Invalid User.')
     return
 
   def save(self):

timer/views.py

@@ -1,10 +1,12 @@
 from django.contrib.auth.models import User, Group
+import django.forms
 from django.shortcuts import render
 import django.views.generic
 from rest_framework import authentication, permissions, status, viewsets
 from rest_framework.generics import CreateAPIView
 from rest_framework.response import Response
 from rest_framework.views import APIView
+from django.http import JsonResponse
 
 import timer.serializers
 import timer.models
@@ -57,8 +59,11 @@ class OfficeHoursFormView(django.views.generic.FormView):
 
   def post(self, request, *args, **kwargs):
     form = self.form_class(**self.get_form_kwargs())
-    if form.is_valid():
+    try:
+      form.is_valid()
       form.save()
+    except django.forms.ValidationError as e:
+      return JsonResponse({'error': e.message}, status=status.HTTP_400_BAD_REQUEST)
 
     return super().post(request, *args, **kwargs)