get-empty-etag.md

when GetObj returns a fake ETag from md5sum /dev/null:

diff --git a/src/rgw/rgw_rest_s3.cc b/src/rgw/rgw_rest_s3.cc
index ccb8a397aec..dbb8576ebbc 100644
--- a/src/rgw/rgw_rest_s3.cc
+++ b/src/rgw/rgw_rest_s3.cc
@@ -445,7 +445,7 @@ int RGWGetObj_ObjStore_S3::send_response_data(bufferlist& bl, off_t bl_ofs,
     } else {
       auto iter = attrs.find(RGW_ATTR_ETAG);
       if (iter != attrs.end()) {
-        dump_etag(s, iter->second.to_str());
+        dump_etag(s, "d41d8cd98f00b204e9800998ecf8427e");

boto: the only test failures were the result of ETag comparisons between GetObject, ListObjects, and PutObject. these would pass if the ops were consistent about this fake-etag behavior

================================================================== short test summary info ===================================================================
FAILED s3tests/functional/test_s3.py::test_atomic_dual_conditional_write_1mb - AssertionError: assert 'AAAAAAAAAAAA...AAAAAAAAAAAAA' == 'BBBBBBBBBBBB...BBBBBBBBBBBBB'
FAILED s3tests_boto3/functional/test_s3.py::test_bucket_list_return_data - assert '"37b51d194a7...f6524f2d51f2"' == '"d41d8cd98f0...0998ecf8427e"'
FAILED s3tests_boto3/functional/test_s3.py::test_bucket_list_return_data_versioning - assert '"37b51d194a7...f6524f2d51f2"' == '"d41d8cd98f0...0998ecf8427e"'
FAILED s3tests_boto3/functional/test_s3.py::test_post_object_success_redirect_action - AssertionError: assert 'http://local...524f2d51f2%22' == 'http://local...98ecf8427e%22'
FAILED s3tests_boto3/functional/test_s3.py::test_put_object_ifmatch_good - botocore.exceptions.ClientError: An error occurred (PreconditionFailed) when calling the PutObject operation: Unknown
FAILED s3tests_boto3/functional/test_s3.py::test_put_object_ifnonmatch_failed - AssertionError: ClientError not raised
================================ 6 failed, 576 passed, 77 skipped, 112 deselected, 1 xfailed, 3 warnings in 287.36s (0:04:47) ================================
ERROR: InvocationError for command /home/cbodley/s3-tests/.tox/py/bin/pytest -m 'not fails_on_rgw and not sse_s3 and not lifecycle_expiration and not test_of_sts and not webidentity_test' (exited with code 1)

's3cmd get' does not try to verify the etag and succeeds