mtr test galera_3nodes.galera_pc_weight fails sporadically in last phase where node 3 is queried for wsrep status variables:

--connection node_3
SELECT VARIABLE_VALUE = 3 FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_cluster_size';
SELECT VARIABLE_VALUE = 3 FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_cluster_weight';
SELECT VARIABLE_VALUE = 'Primary' FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_cluster_status';
SELECT VARIABLE_VALUE = 'ON' FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_connected';
SELECT VARIABLE_VALUE = 'ON' FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_ready';
SELECT VARIABLE_VALUE = 4 FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_local_state';
SELECT VARIABLE_VALUE = 'Synced' FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE VARIABLE_NAME = 'wsrep_local_state_comment';

Probable reason is that node 3 was not 'ready' at the time these queries were issued