Recursively update a dict.

    Subdict's won't be overwritten but also updated.

def deepupdate(original, update):
    """Recursively update a dict.

    Subdict's won't be overwritten but also updated.
    """
    for key, value in original.items():
        if key not in update:
            update[key] = value
        elif isinstance(value, dict):
            deepupdate(value, update[key])
    return update