default void preGetUserPermissions(ObserverContext<MasterCoprocessorEnvironment> ctx,
    String userName, String namespace, TableName tableName, byte[] family, byte[] qualifier)
    throws IOException {
  }
Called before getting user permissions.
@param ctx       the coprocessor instance's environment
@param userName  the user name, null if get all user permissions
@param namespace the namespace, null if don't get namespace permission
@param tableName the table name, null if don't get table permission
@param family    the table column family, null if don't get table family permission
@param qualifier the table column qualifier, null if don't get table qualifier permission
@throws IOException if something went wrong
hbase-server/src/main/java/org/apache/hadoop/hbase/coprocessor/MasterObserver.java