Upgrading Ansible Tower to 3.5. failed on database schema migration stage

Trying to upgrade existing Ansible Tower from version 3.2.5 to 3.5.01 using the bundled installer but ran into the following problem during the upgrade (using setup.sh):

start: ‘2019-06-03 22:57:36.592912’
stderr: |-
Traceback (most recent call last):
File “/bin/awx-manage”, line 11, in
load_entry_point(‘awx==3.5.0’, ‘console_scripts’, ‘awx-manage’)()
File “/init.py”, line 140, in manage
File “/var/lib/awx/venv/awx/lib64/python3.6/site-packages/django/core/management/init.py”, line 364, in execute_from_command_line
utility.execute()
File “/var/lib/awx/venv/awx/lib64/python3.6/site-packages/django/core/management/init.py”, line 356, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File “/var/lib/awx/venv/awx/lib64/python3.6/site-packages/django/core/management/base.py”, line 283, in run_from_argv
self.execute(*args, **cmd_options)
File “/var/lib/awx/venv/awx/lib64/python3.6/site-packages/django/core/management/base.py”, line 330, in execute
output = self.handle(*args, **options)
File “/var/lib/awx/venv/awx/lib64/python3.6/site-packages/django/core/management/commands/migrate.py”, line 204, in handle
fake_initial=fake_initial,
File “/var/lib/awx/venv/awx/lib64/python3.6/site-packages/django/db/migrations/executor.py”, line 115, in migrate
state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
File “/var/lib/awx/venv/awx/lib64/python3.6/site-packages/django/db/migrations/executor.py”, line 145, in _migrate_all_forwards
state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
File “/var/lib/awx/venv/awx/lib64/python3.6/site-packages/django/db/migrations/executor.py”, line 244, in apply_migration
state = migration.apply(state, schema_editor)
File “/var/lib/awx/venv/awx/lib64/python3.6/site-packages/django/db/migrations/migration.py”, line 129, in apply
operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
File “/var/lib/awx/venv/awx/lib64/python3.6/site-packages/django/db/migrations/operations/special.py”, line 193, in database_forwards
self.code(from_state.apps, schema_editor)
File “/var/lib/awx/venv/awx/lib64/python3.6/site-packages/awx/conf/migrations/_ldap_group_type.py”, line 25, in fill_ldap_group_type_params
for k in group_type_params.keys():
RuntimeError: dictionary changed size during iteration
stderr_lines:
stdout: |-
Operations to perform:
Apply all migrations: auth, conf, contenttypes, main, oauth2_provider, sessions, sites, social_django, sso, taggit
Running migrations:
Applying conf.0006_v331_ldap_group_type…
stdout_lines:

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