Migration 0056 is failing

[mdellweg]

# pulpcore-manager migrate
Operations to perform:
  Apply all migrations: ansible, auth, certguard, container, contenttypes, core, deb, file, gem, maven, ostree, python, rpm, sessions
Running migrations:
  Applying ansible.0056_collectionversion_sha256...Traceback (most recent call last):
  File "/usr/local/lib/python3.9/site-packages/django/db/backends/utils.py", line 87, in _execute
    return self.cursor.execute(sql)
  File "/usr/local/lib/python3.9/site-packages/psycopg/cursor.py", line 97, in execute
    raise ex.with_traceback(None)
psycopg.errors.UniqueViolation: could not create unique index "ansible_collectionversion_sha256_a4d120ab_uniq"
DETAIL:  Key (sha256)=() is duplicated.

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/usr/local/bin/pulpcore-manager", line 8, in <module>
    sys.exit(manage())
  File "/usr/local/lib/python3.9/site-packages/pulpcore/app/manage.py", line 11, in manage
    execute_from_command_line(sys.argv)
  File "/usr/local/lib/python3.9/site-packages/django/core/management/__init__.py", line 442, in execute_from_command_line
    utility.execute()
  File "/usr/local/lib/python3.9/site-packages/django/core/management/__init__.py", line 436, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python3.9/site-packages/django/core/management/base.py", line 412, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/usr/local/lib/python3.9/site-packages/django/core/management/base.py", line 458, in execute
    output = self.handle(*args, **options)
  File "/usr/local/lib/python3.9/site-packages/django/core/management/base.py", line 106, in wrapper
    res = handle_func(*args, **kwargs)
  File "/usr/local/lib/python3.9/site-packages/django/core/management/commands/migrate.py", line 356, in handle
    post_migrate_state = executor.migrate(
  File "/usr/local/lib/python3.9/site-packages/django/db/migrations/executor.py", line 135, in migrate
    state = self._migrate_all_forwards(
  File "/usr/local/lib/python3.9/site-packages/django/db/migrations/executor.py", line 167, in _migrate_all_forwards
    state = self.apply_migration(
  File "/usr/local/lib/python3.9/site-packages/django/db/migrations/executor.py", line 252, in apply_migration
    state = migration.apply(state, schema_editor)
  File "/usr/local/lib/python3.9/site-packages/django/db/migrations/migration.py", line 132, in apply
    operation.database_forwards(
  File "/usr/local/lib/python3.9/site-packages/django/db/migrations/operations/models.py", line 659, in database_forwards
    alter_together(
  File "/usr/local/lib/python3.9/site-packages/django/db/backends/base/schema.py", line 563, in alter_unique_together
    self.execute(self._create_unique_sql(model, fields))
  File "/usr/local/lib/python3.9/site-packages/django/db/backends/postgresql/schema.py", line 48, in execute
    return super().execute(sql, None)
  File "/usr/local/lib/python3.9/site-packages/django/db/backends/base/schema.py", line 201, in execute
    cursor.execute(sql, params)
  File "/usr/local/lib/python3.9/site-packages/django/db/backends/utils.py", line 67, in execute
    return self._execute_with_wrappers(
  File "/usr/local/lib/python3.9/site-packages/django/db/backends/utils.py", line 80, in _execute_with_wrappers
    return executor(sql, params, many, context)
  File "/usr/local/lib/python3.9/site-packages/django/db/backends/utils.py", line 89, in _execute
    return self.cursor.execute(sql, params)
  File "/usr/local/lib/python3.9/site-packages/django/db/utils.py", line 91, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "/usr/local/lib/python3.9/site-packages/django/db/backends/utils.py", line 87, in _execute
    return self.cursor.execute(sql)
  File "/usr/local/lib/python3.9/site-packages/psycopg/cursor.py", line 97, in execute
    raise ex.with_traceback(None)
django.db.utils.IntegrityError: could not create unique index "ansible_collectionversion_sha256_a4d120ab_uniq"
DETAIL:  Key (sha256)=() is duplicated.

Originally posted by @netsandbox in #1052 (comment)