def file_safety_check(filename):
    """    Function to check a file and raise an :py:exc:`IOError`
    if it is not "safe."  "Safe" meaning that the file exists and
    it is readable.

    :argument filename:
        The file you wish to check the safety of.
    :type filename: str
    :rtype: None
    :exception:
        :py:exc:`IOError` : Raised when a file is not safe
    """
    with open(filename) as f:
        pass
