Merge remote-tracking branch 'tower/release_3.2.3' into devel

* tower/release_3.2.3:
  fix unicode bugs with log statements
  use --export option for ansible-inventory
  add support for new "BECOME" prompt in Ansible 2.5+ for adhoc commands
  enforce strings for secret password inputs on Credentials
  fix a bug for "users should be able to change type of unused credential"
  fix xss vulnerabilities - on host recent jobs popover - on schedule name tooltip
  fix a bug when testing UDP-based logging configuration
  bump templates form credential_types page limit
  Wait for Slack RTM API websocket connection to be established
  don't process artifacts from custom `set_stat` calls asynchronously
  don't overwrite env['ANSIBLE_LIBRARY'] when fact caching is enabled
  only allow facts to cache in the proper file system location
  replace our memcached-based fact cache implementation with local files
  add support for new "BECOME" prompt in Ansible 2.5+
  fix a bug in inventory generation for isolated nodes
  properly handle unicode for isolated job buffers

awx/main/fields.py

@@ -506,6 +506,12 @@ class CredentialInputField(JSONSchemaField):
                 v != '$encrypted$',
                 model_instance.pk
             ]):
+                if not isinstance(getattr(model_instance, k), six.string_types):
+                    raise django_exceptions.ValidationError(
+                        _('secret values must be of type string, not {}').format(type(v).__name__),
+                        code='invalid',
+                        params={'value': v},
+                    )
                 decrypted_values[k] = utils.decrypt_field(model_instance, k)
             else:
                 decrypted_values[k] = v