Prints message that no files were found in the input directory with the
    given list of extensions.

    :param opts: Namespace object created from command-line arguments. Must
    have the attributes 'extensions' and 'input'

def print_no_files_found(opts):
    """
    Prints message that no files were found in the input directory with the
    given list of extensions.

    :param opts: Namespace object created from command-line arguments. Must
    have the attributes 'extensions' and 'input'
    """
    msg =  "No files found with [" +', '.join(opts.extensions) + "] "
    msg += "extension" +("s " if len(opts.extensions) > 1 else " ")
    msg += "in " + opts.input
    # if recursive
    msg += " or any of its subdirectories"
    print(msg)