Handle empty bucket while nuking

Signed-off-by: Andrew Gaul <andrew@gaul.org>

s3tests/functional/__init__.py

@@ -70,7 +70,10 @@ def nuke_prefixed_buckets_on_conn(prefix, name, conn):
                     try:
                         iterator = iter(bucket.list_versions())
                         # peek into iterator to issue list operation
+                        try:
                             keys = itertools.chain([next(iterator)], iterator)
+                        except StopIteration:
+                            keys = []  # empty iterator
                     except boto.exception.S3ResponseError as e:
                         # some S3 implementations do not support object
                         # versioning - fall back to listing without versions