code: public CommandLine setExecutionExceptionHandler(IExecutionExceptionHandler executionExceptionHandler) {
          this.executionExceptionHandler = Assert.notNull(executionExceptionHandler, "executionExceptionHandler");
          for (CommandLine sub : getSubcommands().values()) { sub.setExecutionExceptionHandler(executionExceptionHandler); }
          return this;
      }
docs: Sets a custom handler for dealing with exceptions that occurred in the {@code Callable}, {@code Runnable} or {@code Method}
  user object of a command when the command was executed via the {@linkplain #execute(String...) execute} method.
  <p>Implementors may be interested in the {@link PicocliException#rethrowCauseIf(Class)} method.</p>
  @param executionExceptionHandler the handler for dealing with exceptions that occurred in the business logic when the {@link #execute(String...) execute} method was invoked.
  @return this CommandLine for method chaining
  @since 4.0