Internal auth upgrade dtest failing on trunk

ERROR [SharedPool-Worker-2] 2015-07-01 08:41:09,779 Message.java:611 - Unexpected exception during request; channel = [id: 0xe7d58967, /127.0.0.1:44390 => /127.0.0.1:9042]
java.lang.UnsupportedOperationException: null
    at org.apache.cassandra.db.ReadCommand$Serializer.serializedSize(ReadCommand.java:505) ~[main/:na]
    at org.apache.cassandra.db.ReadCommand$Serializer.serializedSize(ReadCommand.java:446) ~[main/:na]
    at org.apache.cassandra.net.MessageOut.payloadSize(MessageOut.java:166) ~[main/:na]
    at org.apache.cassandra.net.OutboundTcpConnectionPool.getConnection(OutboundTcpConnectionPool.java:67) ~[main/:na]
    at org.apache.cassandra.net.MessagingService.getConnection(MessagingService.java:551) ~[main/:na]
    at org.apache.cassandra.net.MessagingService.sendOneWay(MessagingService.java:698) ~[main/:na]
    at org.apache.cassandra.net.MessagingService.sendRR(MessagingService.java:641) ~[main/:na]
    at org.apache.cassandra.net.MessagingService.sendRRWithFailure(MessagingService.java:624) ~[main/:na]
    at org.apache.cassandra.service.AbstractReadExecutor.makeRequests(AbstractReadExecutor.java:104) ~[main/:na]
    at org.apache.cassandra.service.AbstractReadExecutor.makeDataRequests(AbstractReadExecutor.java:77) ~[main/:na]
    at org.apache.cassandra.service.AbstractReadExecutor$NeverSpeculatingReadExecutor.executeAsync(AbstractReadExecutor.java:208) ~[main/:na]
    at org.apache.cassandra.service.StorageProxy$SinglePartitionReadLifecycle.doInitialQueries(StorageProxy.java:1424) ~[main/:na]
    at org.apache.cassandra.service.StorageProxy.fetchRows(StorageProxy.java:1379) ~[main/:na]
    at org.apache.cassandra.service.StorageProxy.readRegular(StorageProxy.java:1326) ~[main/:na]
    at org.apache.cassandra.service.StorageProxy.read(StorageProxy.java:1245) ~[main/:na]
    at org.apache.cassandra.db.SinglePartitionReadCommand$Group.execute(SinglePartitionReadCommand.java:435) ~[main/:na]
    at org.apache.cassandra.cql3.statements.SelectStatement.execute(SelectStatement.java:221) ~[main/:na]
    at org.apache.cassandra.cql3.statements.SelectStatement.execute(SelectStatement.java:191) ~[main/:na]
    at org.apache.cassandra.auth.PasswordAuthenticator.doAuthenticate(PasswordAuthenticator.java:143) ~[main/:na]
    at org.apache.cassandra.auth.PasswordAuthenticator.authenticate(PasswordAuthenticator.java:85) ~[main/:na]
    at org.apache.cassandra.auth.PasswordAuthenticator.access$100(PasswordAuthenticator.java:53) ~[main/:na]
    at org.apache.cassandra.auth.PasswordAuthenticator$PlainTextSaslAuthenticator.getAuthenticatedUser(PasswordAuthenticator.java:181) ~[main/:na]
    at org.apache.cassandra.transport.messages.AuthResponse.execute(AuthResponse.java:78) ~[main/:na]
    at org.apache.cassandra.transport.Message$Dispatcher.channelRead0(Message.java:507) [main/:na]
    at org.apache.cassandra.transport.Message$Dispatcher.channelRead0(Message.java:401) [main/:na]
    at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:333) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.channel.AbstractChannelHandlerContext.access$700(AbstractChannelHandlerContext.java:32) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at io.netty.channel.AbstractChannelHandlerContext$8.run(AbstractChannelHandlerContext.java:324) [netty-all-4.0.23.Final.jar:4.0.23.Final]
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [na:1.8.0_45]
    at org.apache.cassandra.concurrent.AbstractTracingAwareExecutorService$FutureTask.run(AbstractTracingAwareExecutorService.java:164) [main/:na]
    at org.apache.cassandra.concurrent.SEPWorker.run(SEPWorker.java:105) [main/:na]
    at java.lang.Thread.run(Thread.java:745) [na:1.8.0_45]