[TYPO3-project-4-3] Improve error handling for tslib_fe->printError() and die()

[Jeff Segars]

Hey guys,
In the past few weeks we've realized how nice it is to keep an eye on 
client sites by monitoring output from TYPO3's sysLog. It's been really 
convenient as it gives us a quick view of problems that don't 
necessarily generate PHP errors.

The parts that are really nice have opened our eyes to a few areas that 
could use some improvement as well.  Specifically, there are quite a few 
places in the core that just die() without writing anything into the 
sysLog (t3lib_extMgm::extPath() for example).

I'd like to improve this for 4.3 so I've opened up a feature request at 
[1] and will include the text below. I'm curious what ideas you have and 
wonder how exceptions might fit in here too.

Thanks,
Jeff

[1] http://bugs.typo3.org/view.php?id=11501
===========================================

Currently, TYPO3 handles severe errors in two ways. In a frontend 
context, tslib_fe->printError() is used to show a nicely formatted error 
message to the user. The call to printError() is typically accompanied 
by a corresponding sysLog entry and a 404 or 503 header to let the 
browser know this was not the expected result [1]. In the backend 
context, a simple die() is used with no specific headers or sysLog 
entries [2].

I would propose a new printError() method that is valid in both a 
frontend and backend context (the current method is actually a wrapper 
for a method in t3lib_timetrack which makes no sense to me). In addition 
to the current HTML output, it should handle the sysLog entry, HTTP 
headers, and exit. It should also check for CLI mode and output a simple 
text message in this case rather than the full HTML.

[1] From tslib_fe->connectToDB()
$message = 'Cannot connect to the current database, "'.TYPO3_db.'"';
t3lib_div::sysLog($message, 'cms', t3lib_div::SYSLOG_SEVERITY_ERROR);
header('HTTP/1.0 503 Service Temporarily Unavailable');
$this->printError($message, 'Database Error');
exit;

[2] from t3lib_extMgm::extPath()
if (!isset($TYPO3_LOADED_EXT[$key])) {
     #debug(array(debug_backtrace()));
     die('TYPO3 Fatal Error: Extension key "'.$key.'" was NOT loaded! 
(t3lib_extMgm::extPath)');
}