Trim and hash base64 strings

def _trim_base64(s):
    """Trim and hash base64 strings"""
    if len(s) > 64 and _base64.match(s.replace('\n', '')):
        h = hash_string(s)
        s = '%s...<snip base64, md5=%s...>' % (s[:8], h[:16])
    return s