code: def get_consensus_at(block_height, proxy=None, hostport=None):
      
      assert proxy or hostport, 'Need either proxy or hostport'
      if proxy is None:
          proxy = connect_hostport(hostport)
  
      consensus_schema = {
          'type': 'object',
          'properties': {
              'consensus': {
                  'anyOf': [
                      {
                          'type': 'string',
                          'pattern': OP_CONSENSUS_HASH_PATTERN,
                      },
                      {
                          'type': 'null'
                      },
                  ],
              },
          },
          'required': [
              'consensus',
          ],
      }
  
      resp_schema = json_response_schema( consensus_schema )
      resp = {}
      try:
          resp = proxy.get_consensus_at(block_height)
          resp = json_validate(resp_schema, resp)
          if json_is_error(resp):
              return resp
  
      except ValidationError as ve:
          if BLOCKSTACK_DEBUG:
              log.exception(ve)
  
          resp = {'error': 'Server response did not match expected schema.  You are likely communicating with an out-of-date Blockstack node.', 'http_status': 502}
          return resp
  
      except socket.timeout:
          log.error("Connection timed out")
          resp = {'error': 'Connection to remote host timed out.', 'http_status': 503}
          return resp
  
      except socket.error as se:
          log.error("Connection error {}".format(se.errno))
          resp = {'error': 'Connection to remote host failed.', 'http_status': 502}
          return resp
  
      except Exception as ee:
          if BLOCKSTACK_DEBUG:
              log.exception(ee)
  
          log.error("Caught exception while connecting to Blockstack node: {}".format(ee))
          resp = {'error': 'Failed to contact Blockstack node.  Try again with `--debug`.', 'http_status': 500}
          return resp
  
      if resp['consensus'] is None:
          # node hasn't processed this block 
          return {'error': 'The node has not processed block {}'.format(block_height), 'http_status': 503}
  
      return resp['consensus']
docs: Get consensus at a block
      Returns the consensus hash on success
      Returns {'error': ...} on error