Replace greek characters in a string.

def _replace_greek_characters(line):
    """Replace greek characters in a string."""
    for greek_char, replacement in iteritems(_GREEK_REPLACEMENTS):
        try:
            line = line.replace(greek_char, replacement)
        except UnicodeDecodeError:
            current_app.logger.exception("Unicode decoding error.")
            return ""
    return line