Make the clear expired locks commands be compatible with Django >= 1.10

[alexagrf]

NoArgsCommand got removed. Django also doesn't use optparse any more.

Patch is a bit ugly, but it has the benefits of being feature-checking instead of version checking

[Duologic]

Hi @alexagrf

We are trying to get some order in the repository and merged the branch we were using in production into master. Would you mind rebasing your pull request on the current master?

I can then poke some people to review and test.

[alexagrf]

I don't think this patch is needed any more, since you removed that function and moved it to a celery task.
Would it be possible to make celery an optional dependency instead? In that case, this patch could stay for non-celery users like me.

[Duologic]

We could move locking.tasks.clean_expired_locks() to locking.utils and call locking.utils.clean_expired_locks() from both the locking.tasks and the management command. This would make celery and optional requirement to run the clean task.

[Duologic]

FYI, we are also working on Python 2/3 compatibility and supporting multiple Django versions on this branch: #35 This will probably go live pretty soon.