Validate a dictionary containing axiscolor definitions

    Parameters
    ----------
    value: dict
        see :attr:`psyplot.plotter.baseplotter.axiscolor`

    Returns
    -------
    dict

    Raises
    ------
    ValueError

def validate_axiscolor(value):
    """Validate a dictionary containing axiscolor definitions

    Parameters
    ----------
    value: dict
        see :attr:`psyplot.plotter.baseplotter.axiscolor`

    Returns
    -------
    dict

    Raises
    ------
    ValueError"""
    validate = try_and_error(validate_none, validate_color)
    possible_keys = {'right', 'left', 'top', 'bottom'}
    try:
        value = dict(value)
        false_keys = set(value) - possible_keys
        if false_keys:
            raise ValueError("Wrong keys (%s)!" % (', '.join(false_keys)))
        for key, val in value.items():
            value[key] = validate(val)
    except:
        value = dict(zip(possible_keys, repeat(validate(value))))
    return value