Fix borked migration between 3.3.0 and 3.3.1+ schema.

closes: #6743
https://pulp.plan.io/issues/6743
(cherry picked from commit e468ab7)

CHANGES/6743.bugfix

@@ -0,0 +1 @@
+Add a new migration to ensure that 'last_sync_revision_number' is nullable.

pulp_rpm/app/migrations/0005_optimize_sync.py

@@ -25,6 +25,6 @@ class Migration(migrations.Migration):
         migrations.AddField(
             model_name='rpmrepository',
             name='last_sync_revision_number',
-            field=models.CharField(max_length=20, null=True),
+            field=models.CharField(max_length=20),
         ),
     ]

pulp_rpm/app/migrations/0009_revision_null.py

@@ -13,6 +13,6 @@ class Migration(migrations.Migration):
         migrations.AlterField(
             model_name='rpmrepository',
             name='last_sync_revision_number',
-            field=models.CharField(max_length=20, null=True),
+            field=models.CharField(max_length=20),
         ),
     ]

pulp_rpm/app/migrations/0010_revision_null_redo.py

@@ -0,0 +1,18 @@
+# Generated by Django 2.2.12 on 2020-05-06 15:15
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('rpm', '0009_revision_null'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='rpmrepository',
+            name='last_sync_revision_number',
+            field=models.CharField(max_length=20, null=True),
+        ),
+    ]