This function irreversibly destroys a virtual machine on the cloud provider.
    Before doing so, it should fire an event on the Salt event bus.

    The tag for this event is `salt/cloud/<vm name>/destroying`.
    Once the virtual machine has been destroyed, another event is fired.
    The tag for that event is `salt/cloud/<vm name>/destroyed`.

    Dependencies:
        list_nodes

    @param name:
    @type name: str
    @param call:
    @type call:
    @return: True if all went well, otherwise an error message
    @rtype: bool|str

def destroy(name, call=None):
    """
    This function irreversibly destroys a virtual machine on the cloud provider.
    Before doing so, it should fire an event on the Salt event bus.

    The tag for this event is `salt/cloud/<vm name>/destroying`.
    Once the virtual machine has been destroyed, another event is fired.
    The tag for that event is `salt/cloud/<vm name>/destroyed`.

    Dependencies:
        list_nodes

    @param name:
    @type name: str
    @param call:
    @type call:
    @return: True if all went well, otherwise an error message
    @rtype: bool|str
    """
    log.info("Attempting to delete instance %s", name)
    if not vb_machine_exists(name):
        return "{0} doesn't exist and can't be deleted".format(name)

    __utils__['cloud.fire_event'](
        'event',
        'destroying instance',
        'salt/cloud/{0}/destroying'.format(name),
        args={'name': name},
        sock_dir=__opts__['sock_dir'],
        transport=__opts__['transport']
    )

    vb_destroy_machine(name)

    __utils__['cloud.fire_event'](
        'event',
        'destroyed instance',
        'salt/cloud/{0}/destroyed'.format(name),
        args={'name': name},
        sock_dir=__opts__['sock_dir'],
        transport=__opts__['transport']
    )