Fix VM creation with default template

Fixes QubesOS/qubes-issues#2866

qubesadmin/app.py

@@ -248,7 +248,9 @@ class QubesBase(qubesadmin.base.PropertyHolder):
         if not isinstance(cls, str):
             cls = cls.__name__
 
-        if template is not None:
+        if template is qubesadmin.DEFAULT:
+            template = None
+        elif template is not None:
             template = str(template)
 
         if pool and pools:

qubesadmin/tests/app.py

@@ -148,6 +148,17 @@ class TC_10_QubesBase(qubesadmin.tests.QubesTestCase):
         self.assertEqual(vm.__class__.__name__, 'AppVM')
         self.assertAllCalled()
 
+    def test_016_new_template_based_default(self):
+        self.app.expected_calls[('dom0', 'admin.vm.Create.AppVM',
+            None, b'name=new-vm label=red')] = b'0\x00'
+        self.app.expected_calls[('dom0', 'admin.vm.List', None, None)] = \
+            b'0\x00new-vm class=AppVM state=Running\n'
+        vm = self.app.add_new_vm('AppVM', 'new-vm', 'red',
+            template=qubesadmin.DEFAULT)
+        self.assertEqual(vm.name, 'new-vm')
+        self.assertEqual(vm.__class__.__name__, 'AppVM')
+        self.assertAllCalled()
+
     def test_020_get_label(self):
         self.app.expected_calls[('dom0', 'admin.label.List', None, None)] = \
             b'0\x00red\nblue\n'