Fix migrations and style issues

oscar/apps/dashboard/vouchers/forms.py

 from django import forms
-from oscar.core.loading import get_model
 from django.utils.translation import ugettext_lazy as _
 
+from oscar.core.loading import get_model
+from oscar.forms import widgets
+
 Voucher = get_model('voucher', 'Voucher')
 Benefit = get_model('offer', 'Benefit')
 Range = get_model('offer', 'Range')
     type_choices = (
         (Benefit.PERCENTAGE, _('Percentage off of products in range')),
         (Benefit.FIXED, _('Fixed amount off of products in range')),
-        (Benefit.SHIPPING_PERCENTAGE, 
-                _("Discount is a percentage off of the shipping cost")),
+        (Benefit.SHIPPING_PERCENTAGE,
+         _("Discount is a percentage off of the shipping cost")),
         (Benefit.SHIPPING_ABSOLUTE,
-                _("Discount is a fixed amount of the shipping cost")),
+         _("Discount is a fixed amount of the shipping cost")),
         (Benefit.SHIPPING_FIXED_PRICE, _("Get shipping for a fixed price")),
     )
     benefit_type = forms.ChoiceField(

oscar/apps/voucher/abstract_models.py

         return self.name
 
     def clean(self):
-        if (self.start_datetime and self.end_datetime and
-            self.start_datetime > self.end_datetime):
+        if all([self.start_datetime, self.end_datetime,
+                self.start_datetime > self.end_datetime]):
             raise exceptions.ValidationError(
                 _('End date should be later than start date'))
 

oscar/apps/voucher/admin.py

     readonly_fields = ('num_basket_additions', 'num_orders', 'total_discount')
     fieldsets = (
         (None, {
-            'fields': ('name', 'code', 'usage', 'start_datetime', 'end_datetime')}),
+            'fields': ('name', 'code', 'usage', 'start_datetime',
+                       'end_datetime')}),
         ('Benefit', {
             'fields': ('offers',)}),
         ('Usage', {

oscar/apps/voucher/migrations/0002_auto__chg_field_voucher_end_date__chg_field_voucher_start_date.py

 from django.db import models
 from django.utils import timezone
 
+from oscar.core.compat import AUTH_USER_MODEL, AUTH_USER_MODEL_NAME
+
 
 class Migration(SchemaMigration):
     no_dry_run = True
             u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
             'name': ('django.db.models.fields.CharField', [], {'max_length': '50'})
         },
-        u'auth.user': {
-            'Meta': {'object_name': 'User'},
+    AUTH_USER_MODEL: {
+        'Meta': {'object_name': AUTH_USER_MODEL_NAME},
             'date_joined': ('django.db.models.fields.DateTimeField', [], {'default': 'datetime.datetime.now'}),
             'email': ('django.db.models.fields.EmailField', [], {'max_length': '75', 'blank': 'True'}),
             'first_name': ('django.db.models.fields.CharField', [], {'max_length': '30', 'blank': 'True'}),
             'status': ('django.db.models.fields.CharField', [], {'max_length': '100', 'null': 'True', 'blank': 'True'}),
             'total_excl_tax': ('django.db.models.fields.DecimalField', [], {'max_digits': '12', 'decimal_places': '2'}),
             'total_incl_tax': ('django.db.models.fields.DecimalField', [], {'max_digits': '12', 'decimal_places': '2'}),
-            'user': ('django.db.models.fields.related.ForeignKey', [], {'blank': 'True', 'related_name': "'orders'", 'null': 'True', 'to': u"orm['auth.User']"})
+            'user': ('django.db.models.fields.related.ForeignKey', [], {'blank': 'True', 'related_name': "'orders'", 'null': 'True', 'to': u"orm['{0}']".format(AUTH_USER_MODEL)})
         },
         u'order.shippingaddress': {
             'Meta': {'object_name': 'ShippingAddress'},
             'date_created': ('django.db.models.fields.DateField', [], {'auto_now_add': 'True', 'blank': 'True'}),
             u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
             'order': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['order.Order']"}),
-            'user': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['auth.User']", 'null': 'True', 'blank': 'True'}),
+            'user': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['{0}']".format(AUTH_USER_MODEL), 'null': 'True', 'blank': 'True'}),
             'voucher': ('django.db.models.fields.related.ForeignKey', [], {'related_name': "'applications'", 'to': u"orm['voucher.Voucher']"})
         }
     }

oscar/apps/voucher/migrations/0003_auto__del_field_voucher_end_date__del_field_voucher_start_date__add_fi.py

 from south.v2 import SchemaMigration
 from django.db import models
 
+from oscar.core.compat import AUTH_USER_MODEL, AUTH_USER_MODEL_NAME
+
 
 class Migration(SchemaMigration):
     no_dry_run = True
             u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
             'name': ('django.db.models.fields.CharField', [], {'max_length': '50'})
         },
-        u'auth.user': {
-            'Meta': {'object_name': 'User'},
+        AUTH_USER_MODEL: {
+            'Meta': {'object_name': AUTH_USER_MODEL_NAME},
             'date_joined': ('django.db.models.fields.DateTimeField', [], {'default': 'datetime.datetime.now'}),
             'email': ('django.db.models.fields.EmailField', [], {'max_length': '75', 'blank': 'True'}),
             'first_name': ('django.db.models.fields.CharField', [], {'max_length': '30', 'blank': 'True'}),
             'status': ('django.db.models.fields.CharField', [], {'max_length': '100', 'null': 'True', 'blank': 'True'}),
             'total_excl_tax': ('django.db.models.fields.DecimalField', [], {'max_digits': '12', 'decimal_places': '2'}),
             'total_incl_tax': ('django.db.models.fields.DecimalField', [], {'max_digits': '12', 'decimal_places': '2'}),
-            'user': ('django.db.models.fields.related.ForeignKey', [], {'blank': 'True', 'related_name': "'orders'", 'null': 'True', 'to': u"orm['auth.User']"})
+            'user': ('django.db.models.fields.related.ForeignKey', [], {'blank': 'True', 'related_name': "'orders'", 'null': 'True', 'to': u"orm['{0}']".format(AUTH_USER_MODEL)})
         },
         u'order.shippingaddress': {
             'Meta': {'object_name': 'ShippingAddress'},
             'date_created': ('django.db.models.fields.DateField', [], {'auto_now_add': 'True', 'blank': 'True'}),
             u'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
             'order': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['order.Order']"}),
-            'user': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['auth.User']", 'null': 'True', 'blank': 'True'}),
+            'user': ('django.db.models.fields.related.ForeignKey', [], {'to': u"orm['{0}']".format(AUTH_USER_MODEL), 'null': 'True', 'blank': 'True'}),
             'voucher': ('django.db.models.fields.related.ForeignKey', [], {'related_name': "'applications'", 'to': u"orm['voucher.Voucher']"})
         }
     }