Change AWS_DEFAULT_ACL to 'private'

[jonashaag]

1. For obvious security reasons
2. Because it doesn't work out of the box with the default S3 tutorial (which doesn't grant publish permissions), with no good error message ("Access Denied", where a good message would be "Access to make file public-read denied")

[jschneier]

I agree, will have to go in a 2.0 release. I've been lax about breaking changes because they are usually smaller and not in widely used backends. This would not be that in any way.

[robatwave]

By default it shouldn't set ACL at all (boto's default behaviour), and defer to the bucket's ACL? Or as a non-breaking change, there should be an option to not explicitly set an ACL on the object. That way you could give an application's IAM role PutObject without having to also give it PutObjectAcl.

[robatwave]

Just to follow up: looks like we can work around this by explicitly setting AWS_DEFAULT_ACL to None in settings.

[jschneier]

We will now warn about the insecure defaults with a recommendation to update.