Problem you have encountered:

Projection queries are broken in dev_appserver.py starting with cloud sdk 468.0.0. In the application code the projection query always returns an empty list, and the log is spammed with:

ERROR:root:Exception while handling datastore_v3.RunQuery()
Traceback (most recent call last):
  File "<string>", line 468, in _handle_POST
  File "<string>", line 193, in _execute_request
  File "<string>", line 184, in make_request
  File "/usr/lib64/google-cloud-sdk/platform/google_appengine/google/appengine/datastore/datastore_sqlite_stub.py", line 978, in MakeSyncCall
    apiproxy_stub.APIProxyStub.MakeSyncCall(self, service, call, request,
  File "/usr/lib64/google-cloud-sdk/platform/google_appengine/google/appengine/api/apiproxy_stub.py", line 143, in MakeSyncCall
    method(request, response)
  File "/usr/lib64/google-cloud-sdk/platform/google_appengine/google/appengine/datastore/datastore_stub_util.py", line 3072, in UpdateIndexesWrapper
    return func(self, *args, **kwargs)
  File "/usr/lib64/google-cloud-sdk/platform/google_appengine/google/appengine/datastore/datastore_stub_util.py", line 3363, in _Dynamic_RunQuery
    cursor = self._datastore.GetQueryCursor(query, self._trusted, self._app_id)
  File "/usr/lib64/google-cloud-sdk/platform/google_appengine/google/appengine/datastore/datastore_stub_util.py", line 2639, in GetQueryCursor
    return self._GetQueryCursor(raw_query, filters, orders, index_list)
  File "/usr/lib64/google-cloud-sdk/platform/google_appengine/google/appengine/datastore/datastore_sqlite_stub.py", line 1393, in _GetQueryCursor
    index_list, list(db_cursor))
  File "/usr/lib64/google-cloud-sdk/platform/google_appengine/google/appengine/datastore/datastore_sqlite_stub.py", line 266, in _ProjectionPartialEntityGenerator
    entity.key.MergeFrom(original_entity.key())
TypeError: 'Reference' object is not callable

Steps to reproduce:

Install cloud sdk 468.0.0 and try a ndb projection query in dev_appserver.py

Other information (workarounds you have tried, documentation consulted, etc):

This is broken starting sdk 468, presumably due to the removal of python2 support. For reference, the orginating line 266 in cloud sdk 467

    entity = entity_pb.EntityProto()
    entity.mutable_key().MergeFrom(original_entity.key())
    entity.mutable_entity_group().MergeFrom(original_entity.entity_group())

was changed in cloud sdk 468 to:

    entity = entity_pb2.EntityProto()
    entity.key.MergeFrom(original_entity.key())
    entity.entity_group.MergeFrom(original_entity.entity_group)