add new credential types in a more stable way in migrations

instead of writing individual migrations for new built-in credential
types, this change makes the "setup_tower_managed_defaults" function
idempotent so that it only adds the credential types you're missing

awx/main/migrations/_credentialtypes.py

@@ -175,4 +175,4 @@ def migrate_job_credentials(apps, schema_editor):
 
 
 def create_ovirt4_credtype(apps, schema_editor):
-    CredentialType.defaults['ovirt4']().save()
+    CredentialType.setup_tower_managed_defaults()

awx/main/models/credential.py

@@ -3,6 +3,7 @@
 from collections import OrderedDict
 import functools
 import json
+import logging
 import operator
 import os
 import stat
@@ -35,6 +36,8 @@ from awx.main.utils import encrypt_field
 
 __all__ = ['Credential', 'CredentialType', 'V1Credential']
 
+logger = logging.getLogger('awx.main.models.credential')
+
 
 class V1Credential(object):
 
@@ -468,6 +471,11 @@ class CredentialType(CommonModelNameNotUnique):
         for default in cls.defaults.values():
             default_ = default()
             if persisted:
+                if CredentialType.objects.filter(name=default_.name, kind=default_.kind).count():
+                    continue
+                logger.debug(_(
+                    "adding %s credential type" % default_.name
+                ))
                 default_.save()
 
     @classmethod

awx/main/tests/functional/api/test_credential.py

@@ -14,6 +14,17 @@ EXAMPLE_PRIVATE_KEY = '-----BEGIN PRIVATE KEY-----\nxyz==\n-----END PRIVATE KEY-
 EXAMPLE_ENCRYPTED_PRIVATE_KEY = '-----BEGIN PRIVATE KEY-----\nProc-Type: 4,ENCRYPTED\nxyz==\n-----END PRIVATE KEY-----'
 
 
+@pytest.mark.django_db
+def test_idempotent_credential_type_setup():
+    assert CredentialType.objects.count() == 0
+    CredentialType.setup_tower_managed_defaults()
+    total = CredentialType.objects.count()
+    assert total > 0
+
+    CredentialType.setup_tower_managed_defaults()
+    assert CredentialType.objects.count() == total
+
+
 @pytest.mark.django_db
 @pytest.mark.parametrize('kind, total', [
     ('ssh', 1), ('net', 0)