$HOST string appears in 'Not my vbucket' error response

I have a 4node cluster in cluster_run
1) start rebalance
2) try to do sets

• get MemcachedError 'not my vbucket'
  3) try to update vbucketmap
• serverList contains $HOST strings and automation tries to look at the serverList and then fails to update vbucket_map

,"serverList":["192.168.1.3:12000","$HOST:12002","$HOST:12004","$HOST:12006"],

reproduced with mc_bin client during rebalance.
>>> mc=mc_bin_client.MemcachedClient(port=12000)
>>> mc.set('hello',0,0,'world',1023)

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "mc_bin_client.py", line 163, in set
return self._mutate(memcacheConstants.CMD_SET, key, exp, flags, 0, val)
File "mc_bin_client.py", line 132, in _mutate
cas)
File "mc_bin_client.py", line 128, in _doCmd
return self._handleSingleResponse(opaque)
File "mc_bin_client.py", line 121, in _handleSingleResponse
cmd, opaque, cas, keylen, extralen, data = self._handleKeyedResponse(myopaque)
File "mc_bin_client.py", line 117, in _handleKeyedResponse
raise MemcachedError(errcode, rv)
mc_bin_client.MemcachedError: Memcached error #7 'Not my vbucket': {"rev":216,"name":"default","uri":"/pools/default/buckets/default?bucket_uuid=d208f8f354a3cb3c8cbe7c02d2d542f9","streamingUri":"/pools/default/bucketsStreaming/default?bucket_uuid=d208f8f354a3cb3c8cbe7c02d2d542f9","nodes":[{"couchApiBase":"http://$HOST:9502/default","hostname":"$HOST:9002","ports":{"proxy":12005,"direct":12004}},{"couchApiBase":"http://$HOST:9503/default","hostname":"$HOST:9003","ports":{"proxy":12007,"direct":12006}},{"couchApiBase":"http://$HOST:9501/default","hostname":"$HOST:9001","ports":{"proxy":12003,"direct":12002}},{"couchApiBase":"http://192.168.1.3:9500/default","hostname":"192.168.1.3:9000","ports":{"proxy":12001,"direct":12000}}],"nodeLocator":"vbucket","uuid":"d208f8f354a3cb3c8cbe7c02d2d542f9","bucketCapabilitiesVer":"","bucketCapabilities":["touch","couchapi"],"ddocs":

,"vBucketServerMap":{"hashAlgorithm":"CRC","numReplicas":1,"serverList":["192.168.1.3:12000","$HOST:12002","$HOST:12004","$HOST:12006"],
"vBucketMap":[[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1],[0,-1]
….