static String createRulesFile(String file) throws IOException {
    return createRulesFile(file, Collections.emptyList());
  }
Create rule file with empty rules.
@param file Name of file to write rules into.
@return Full file name of the rules file which is <code>dir</code> + DEFAULT_RULES_FILE_NAME.
hbase-balancer/src/test/java/org/apache/hadoop/hbase/master/balancer/HeterogeneousCostRulesTestHelper.java