Fixed typos and a little phrasing. (#175)

Mostly in German translation, some small fixes in English text, too.

src/pretix/base/models/items.py

@@ -180,7 +180,7 @@ class Item(LoggedModel):
                     'either directly or via a quota.')
     )
     hide_without_voucher = models.BooleanField(
-        verbose_name=_('This product will only be shown if a voucher is redeemed.'),
+        verbose_name=_('This product will only be shown if a voucher matching the product is redeemed.'),
         default=False,
         help_text=_('This product will be hidden from the event page until the user enters a voucher '
                     'code that is specifically tied to this product (and not via a quota).')

src/pretix/base/models/orders.py

@@ -248,7 +248,7 @@ class Order(LoggedModel):
 
     def _is_still_available(self) -> Union[bool, str]:
         error_messages = {
-            'unavailable': _('Some of the ordered products were no longer available.'),
+            'unavailable': _('Some of the ordered products are no longer available.'),
         }
         positions = self.positions.all().select_related('item', 'variation')
         quota_cache = {}

src/pretix/base/services/cart.py

@@ -22,11 +22,11 @@ error_messages = {
               'server was too busy. Please try again.'),
     'empty': _('You did not select any products.'),
     'not_for_sale': _('You selected a product which is not available for sale.'),
-    'unavailable': _('Some of the products you selected were no longer available. '
+    'unavailable': _('Some of the products you selected are no longer available. '
                      'Please see below for details.'),
-    'in_part': _('Some of the products you selected were no longer available in '
+    'in_part': _('Some of the products you selected are no longer available in '
                  'the quantity you selected. Please see below for details.'),
-    'max_items': _("You cannot select more than %s items per order"),
+    'max_items': _("You cannot select more than %s items per order."),
     'not_started': _('The presale period for this event has not yet started.'),
     'ended': _('The presale period has ended.'),
     'voucher_invalid': _('This voucher code is not known in our database.'),

src/pretix/base/services/orders.py

@@ -142,7 +142,7 @@ def cancel_order(order, user=None):
         user = User.objects.get(pk=user)
     with order.event.lock():
         if order.status not in (Order.STATUS_PENDING, Order.STATUS_EXPIRED):
-            raise OrderError(_('You cannot cancel this order'))
+            raise OrderError(_('You cannot cancel this order.'))
         order.status = Order.STATUS_CANCELLED
         order.save()