failed to parse RSS feed

UTF-8 validation can be done, but it would only be useful for latin-using languages with not much accents or non-ASCII letters. Otherwise so much text will be lost that it will be unreadable. Fixing the error on their site is a whopping 5 minutes of work and involves adding the right encoding="..." attribute to their feed. Nothing more.

If you really want to validate UTF-8, you can use this snippet which I wrote. You could invoke it in drupal_xml_parser_create().

function validate_utf8($text) {
  // First pass: find bad sequences
  $text = preg_replace('@(?:'.
    // Invalid bytes
    '[\xFE-\xFF]|'.
    // Ranges not part of Unicode spec
    '\xF4[\x90-\xBF][\x80-\xBF]{2}|'.  //  U+110000 -   U+1FFFFF
    '[\xF5-\xF7][\x80-\xBF]{3}|'.
    '[\xF8-\xFB][\x80-\xBF]{0,4}|'.    //  U+200000 -  U+3FFFFFF
    '[\xFC-\xFD][\x80-\xBF]{0,5}|'.    // U+4000000 - U+7FFFFFFF
    // Unnecessarily long sequences
    '[\xC0-\xC1][\x80-\xBF]|'.
    '\xE0[\x80-\x9F][\x80-\xBF]|'.
    '\xF0[\x80-\x8F][\x80-\xBF]{2}|'.
    // Sequences that are too short
    '[\xC0-\xF7](?![\x80-\xBF])|'.
    '[\xE0-\xF7][\x80-\xBF](?![\x80-\xBF])|'.
    '[\xF0-\xF7][\x80-\xBF]{2}(?![\x80-\xBF])|'.
    // Invalid characters
    '\xED[\xA0-\xBF][\x80-\xBF]|'.     // UTF-16 surrogates
    '\xEF\xBF[\xBE-\xBF]'.             // U+FFFE / U+FFFF
    ')@', '�', $text);

  // Second pass: clean up invalid continuation bytes
  $text = preg_replace_callback('@'.
     // Any normal character sequence
     '(^|[\x00-\x7F]|[\xC0-\xDF][\x80-\xBF]{2}|'.
     '[\xE0-\xEF][\x80-\xBF]{3}|[\xF0-\xF7][\x80-\xBF]{4})'.
     // ...followed directly by continuation bytes.
     '([\x80-\xBF]+)@', '_validate_utf8', $text);

  return $text;
}

function _validate_utf8($matches) {
  return $matches[1] . str_repeat('�', strlen($matches[2]));
}

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