[s3] Deprecate additional settings (#829)

docs/backends/amazon-S3.rst

@@ -87,6 +87,11 @@ To allow ``django-admin.py`` collectstatic to automatically put your static file
 ``AWS_S3_ENCRYPTION`` (optional; default is ``False``)
     Enable server-side file encryption while at rest.
 
+.. deprecated:: 1.9
+
+   Support for this top level setting is deprecated. The functionality is still available by setting
+   ServerSideEncryption=AES256 in AWS_S3_OBJECT_PARAMETERS.
+
 ``AWS_S3_FILE_OVERWRITE`` (optional: default is ``True``)
     By default files with the same name will overwrite each other. Set this to ``False`` to have extra characters appended.
 

storages/backends/s3boto3.py

@@ -283,6 +283,27 @@ def __init__(self, acl=None, bucket=None, **settings):
                 "Unset AWS_AUTO_CREATE_BUCKET (it defaults to False) to silence this warning.",
                 DeprecationWarning,
             )
+        if self.reduced_redundancy:
+            warnings.warn(
+                "Support for AWS_REDUCED_REDUNDANCY will be removed in version 2.0. "
+                "Update now by adding StorageClass=REDUCED_REDUNDANCY to "
+                "AWS_S3_OBJECT_PARAMETERS. There are also several other possible values "
+                "for StorageClass available. Check the AWS & boto3 docs for more info.",
+                DeprecationWarning,
+            )
+        if self.encryption:
+            warnings.warn(
+                "Support for AWS_S3_ENCRYPTION will be removed in version 2.0. "
+                "Update now by adding ServerSideEncryption=AES256 to "
+                "AWS_S3_OBJECT_PARAMETERS. Doing so also easily allows using 'aws:kms' "
+                "for encryption. Check the AWS & boto3 docs for more info.",
+                DeprecationWarning,
+            )
+        if self.preload_metadata:
+            warnings.warn(
+                "Support for AWS_PRELOAD_METADATA will be removed in version 2.0. ",
+                DeprecationWarning,
+            )
 
         check_location(self)