A rather poor way of telling whether an axis has a colorbar associated:
    Check the next axis environment, and see if it is de facto a color bar;
    if yes, return the color bar object.

def _find_associated_colorbar(obj):
    """A rather poor way of telling whether an axis has a colorbar associated:
    Check the next axis environment, and see if it is de facto a color bar;
    if yes, return the color bar object.
    """
    for child in obj.get_children():
        try:
            cbar = child.colorbar
        except AttributeError:
            continue
        if cbar is not None:  # really necessary?
            # if fetch was successful, cbar contains
            # (reference to colorbar,
            #   reference to axis containing colorbar)
            return cbar
    return None