Do not use "guru" as debug level.

See this code from gnupg:

  else if (!strcmp (level, "guru") || numok)
    {
      opt.debug = ~0;
      /* Unless the "guru" string has been used we don't want to allow
         hashing debugging.  The rationale is that people tend to
         select the highest debug value and would then clutter their
         disk with debug files which may reveal confidential data.  */
      if (numok)
        opt.debug &= ~(DBG_HASHING_VALUE);
    }