slapos_panel: show the issue when it is not possible to add a virtual master

master/bt5/slapos_panel/SkinTemplateItem/portal_skins/slapos_panel/Person_addVirtualMaster.py

@@ -14,7 +14,19 @@ project.validate()
 currency_value = portal.restrictedTraverse(price_currency)
 
 # create the subscription request, which will lead to the Open Order
-subscription_request = resource.Resource_createSubscriptionRequest(customer, [], project, currency_value=currency_value)
+try:
+  subscription_request = resource.Resource_createSubscriptionRequest(customer, [], project, currency_value=currency_value)
+except AssertionError, e:
+  if batch:
+    raise
+  return context.Base_redirect(
+    keep_items={
+      'portal_status_level': 'error',
+      'portal_status_message': str(e)
+    },
+    abort_transaction=True,
+  )
+
 
 # XXX How to specify the trade condition containing the currency and trade model lines?
 specialise_value = subscription_request.getSpecialiseValue(portal_type="Sale Trade Condition")