Make use of 'current' apps so RBAC ImplicitRoleField can work during migrations

While a migration is taking place, we can't juse use normal model
references like Role and RolePermission, nor can we use generic foreign
keys without manually referring to the content type and object id
fields.

awx/main/fields.py

@@ -17,10 +17,11 @@ from django.db.models.fields.related import (
     ReverseManyRelatedObjectsDescriptor,
 )
 from django.utils.encoding import smart_text
+from django.utils.timezone import now
 
 # AWX
-from awx.main.models.rbac import RolePermission, Role, batch_role_ancestor_rebuilding
-
+from awx.main.models.rbac import Role, batch_role_ancestor_rebuilding
+from awx.main.utils import get_current_apps
 
 __all__ = ['AutoOneToOneField', 'ImplicitRoleField']
 
@@ -65,8 +66,12 @@ def resolve_role_field(obj, field):
     else:
         return []
 
+    if obj is None:
+        return []
+
     if len(field_components) == 1:
-        if type(obj) is not ImplicitRoleDescriptor and type(obj) is not Role:
+        Role_ = get_current_apps().get_model('main', 'Role')
+        if type(obj) is not ImplicitRoleDescriptor and type(obj) is not Role_:
             raise Exception(smart_text('{} refers to a {}, not an ImplicitRoleField or Role'.format(field, type(obj))))
         ret.append(obj)
     else:
@@ -174,7 +179,10 @@ class ImplicitRoleField(models.ForeignKey):
         role = getattr(instance, self.name, None)
         if role:
             return role
-        role = Role.objects.create(
+        Role_ = get_current_apps().get_model('main', 'Role')
+        role = Role_.objects.create(
+            created=now(),
+            modified=now(),
             name=self.role_name,
             description=self.role_description
         )
@@ -186,9 +194,16 @@ class ImplicitRoleField(models.ForeignKey):
         role.save()
 
         if self.permissions is not None:
-            permissions = RolePermission(
+            RolePermission_ = get_current_apps().get_model('main', 'RolePermission')
+            ContentType = get_current_apps().get_model('contenttypes', "ContentType")
+            instance_content_type = ContentType.objects.get_for_model(instance)
+
+            permissions = RolePermission_(
+                created=now(),
+                modified=now(),
                 role=role,
-                resource=instance,
+                content_type=instance_content_type,
+                object_id=instance.id,
                 auto_generated=True
             )
 
@@ -253,7 +268,20 @@ class ImplicitRoleField(models.ForeignKey):
         parent_roles = set()
         for path in paths:
             if path.startswith("singleton:"):
-                parents = [Role.singleton(path[10:])]
+                singleton_name = path[10:]
+                Role_ = get_current_apps().get_model('main', 'Role')
+                qs = Role_.objects.filter(singleton_name=singleton_name)
+                if qs.count() >= 1:
+                    role = qs[0]
+                else:
+                    role = Role_.objects.create(
+                               created=now(),
+                               modified=now(),
+                               singleton_name=singleton_name,
+                               name=singleton_name,
+                               description=singleton_name
+                           )
+                parents = [role]
             else:
                 parents = resolve_role_field(instance, path)
             for parent in parents: