Some errors are fatal and prevent the script from running at all.
The most common are specifying a nonexistent script (i.e. an incorrect
URL), or fatal compile errors.  These errors can be captured by an
ErrorScript specified in the texis.ini file.  See
here for details.
  Note that a few severe errors, such as stack overflow, can occur
after the script starts (so ErrorScript does not apply),
yet cannot be captured by <putmsg> at all, because the script
cannot continue execution to call <putmsg>.