Fix migration bug

Bump migration number

Skip data migration for fresh migrations
  where ContentType for custom inventory scripts
  has not yet been created
    no scripts will exist in this case, so no-op

awx/main/migrations/0137_custom_inventory_scripts_removal_data.py

@@ -10,7 +10,7 @@ from awx.main.migrations._inventory_source import delete_custom_inv_source
 class Migration(migrations.Migration):
 
     dependencies = [
-        ('main', '0135_schedule_sort_fallback_to_id'),
+        ('main', '0136_scm_track_submodules'),
     ]
 
     operations = [

awx/main/migrations/0138_custom_inventory_scripts_removal.py

@@ -6,7 +6,7 @@ from django.db import migrations, models
 class Migration(migrations.Migration):
 
     dependencies = [
-        ('main', '0136_custom_inventory_scripts_removal_data'),
+        ('main', '0137_custom_inventory_scripts_removal_data'),
     ]
 
     operations = [

awx/main/migrations/_rbac.py

@@ -50,7 +50,10 @@ def delete_all_user_roles(apps, schema_editor):
 def delete_all_custom_script_roles(apps, schema_editor):
     ContentType = apps.get_model('contenttypes', "ContentType")
     Role = apps.get_model('main', "Role")
-    cis_type = ContentType.objects.get(model='custominventoryscript')
+    try:
+        cis_type = ContentType.objects.get(model='custominventoryscript')
+    except ContentType.DoesNotExist:
+        return
     role_ct = 0
     for role in Role.objects.filter(content_type=cis_type).iterator():
         role.delete()