message: Enable to debug node creation backtrace.
diff: @@ -1320,6 +1320,8 @@ class _BaseNodeType(type, metaclass = _BaseNodeTypeType):
  raise Exception('%s %s redefined as a %s' % fmt)
  return node
  +_DEBUG_NODE_CREATION = \
  + [v for v in os.environ.get('DRAKE_DEBUG_NODE_CREATION', '').split(',') if v]
  class BaseNode(object, metaclass = _BaseNodeType):
  @@ -1340,6 +1342,11 @@ class BaseNode(object, metaclass = _BaseNodeType):
  def __init__(self, name):
  """Create a node with the given name."""
  self.__name = name = name.canonize()
  + for n in _DEBUG_NODE_CREATION:
  + if self.__name == n:
  + import traceback
  + print('{} was instantiated at (most recent call last):'.format(self))
  + traceback.print_stack()
  if next(iter(name)) == '..':
  raise Exception('%s is outside the build directory' % name)
  if Drake.current.nodes.setdefault(self.__name, self) is not self:
  