element-info -d ubuntu errors

$ bin/element-info -d ubuntu
Traceback (most recent call last):
  File "bin/element-info", line 23, in <module>
    sys.exit(main(sys.argv))
  File "/home/robertc/work/diskimage-builder/bin/diskimage_builder/element_dependencies.py", line 92, in main
    print(' '.join(expand_dependencies(args.elements)))
  File "/home/robertc/work/diskimage-builder/bin/diskimage_builder/element_dependencies.py", line 74, in expand_dependencies
    deps = dependencies(element, elements_dir)
  File "/home/robertc/work/diskimage-builder/bin/diskimage_builder/element_dependencies.py", line 38, in dependencies
    elements_dir = get_elements_dir()
  File "/home/robertc/work/diskimage-builder/bin/diskimage_builder/element_dependencies.py", line 23, in get_elements_dir
    raise Exception("$ELEMENTS_PATH must be set.")
Exception: $ELEMENTS_PATH must be set.

The rest of the user accessible commands (those we document in README.md) auto-include the dib elements tree in ELEMENTS_PATH, so this is inconsistent.