edit original migration file, add blank string as acceptable to model

awx/main/migrations/0126_executionenvironment_container_options.py

@@ -13,6 +13,6 @@ class Migration(migrations.Migration):
         migrations.AddField(
             model_name='executionenvironment',
             name='pull',
-            field=models.CharField(choices=[('always', 'Always pull container before running.'), ('missing', 'No pull option has been selected.'), ('never', 'Never pull container before running.')], default='missing', help_text='Pull image before running?', max_length=1024),
+            field=models.CharField(choices=[('always', 'Always pull container before running.'), ('missing', 'No pull option has been selected.'), ('never', 'Never pull container before running.')], blank=True, default='', help_text='Pull image before running?', max_length=16),
         ),
     ]

awx/main/migrations/0128_set_default_pull_to_none.py

@@ -1,18 +0,0 @@
-# Generated by Django 2.2.16 on 2021-02-16 20:38
-
-from django.db import migrations, models
-
-
-class Migration(migrations.Migration):
-
-    dependencies = [
-        ('main', '0127_reset_pod_spec_override'),
-    ]
-
-    operations = [
-        migrations.AlterField(
-            model_name='executionenvironment',
-            name='pull',
-            field=models.CharField(choices=[('always', 'Always pull container before running.'), ('missing', 'No pull option has been selected.'), ('never', 'Never pull container before running.')], default=None, help_text='Pull image before running?', max_length=1024),
-        ),
-    ]

awx/main/models/execution_environments.py

@@ -42,9 +42,10 @@ class ExecutionEnvironment(CommonModel):
         on_delete=models.SET_NULL,
     )
     pull = models.CharField(
-        max_length=1024,
+        max_length=16,
         choices=PULL_CHOICES,
-        default=None,
+        blank=True,
+        default='',
         help_text=_('Pull image before running?'),
     )