Setting config.EXPIRE_DEFAULT to "never" breaks cleanup_snippets script

[lyrixderaven]

Description

For a production instance in which the default for expiration should be 'never' - so this entry in the dropdown is also preselected - the cleanup_snippets management script fails, since it relies on an integer value in the config.EXPIRE_DEFAULT setting.

Environment

Both dockerized setup (containers via docker hub) and local development via docker-compose.

Steps to reproduce

1. Edit dpaste/settings/local.py and add the following custom ProductionDpasteAppConfig:

from dpaste.apps import dpasteAppConfig
from django.utils.translation import gettext_lazy as _

class ProductionDpasteAppConfig(dpasteAppConfig):

    EXPIRE_DEFAULT = "never"

INSTALLED_APPS.remove('dpaste.apps.dpasteAppConfig')
INSTALLED_APPS.append('dpaste.settings.local.ProductionDpasteAppConfig')

2. Start your instance (e.g., via docker-compose up
3. Run the cleanup_snippets script (e.g., via docker-compose exec app ./manage.py cleanup_snippets

Expected result

The script currently joins two queries - one for snippets with an expire time set, and one for onetime snippets that haven't yet been viewed. It is the second query that fails to build:

Snippet.objects.filter(
                    expire_type=Snippet.EXPIRE_ONETIME,
                    published__lte=(
                        timezone.now() - timedelta(seconds=config.EXPIRE_DEFAULT)
                    ),
                )

IMHO that script should, in case the EXPIRE_DEFAULT isn't set to an int value, simply omit checking for these one-time snippets.

Actual result

Here's the stacktrace:

Traceback (most recent call last):
  File "/app/manage.py", line 34, in <module>
    main()
  File "/app/manage.py", line 30, in main
    execute_from_command_line(sys.argv)
  File "/usr/local/lib/python3.6/site-packages/django/core/management/__init__.py", line 419, in execute_from_command_line
    utility.execute()
  File "/usr/local/lib/python3.6/site-packages/django/core/management/__init__.py", line 413, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python3.6/site-packages/django/core/management/base.py", line 354, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/usr/local/lib/python3.6/site-packages/django/core/management/base.py", line 398, in execute
    output = self.handle(*args, **options)
  File "/app/dpaste/management/commands/cleanup_snippets.py", line 38, in handle
    timezone.now() - timedelta(seconds=config.EXPIRE_DEFAULT)
TypeError: unsupported type for timedelta seconds component: str