Drupal bootstrap failures should throw debuggable exception

[ErichBSchulz]

Updated Description

Suppose one is submitting a request to a backend entry-point (such as rest.php or cv). If the system an incompatible/incomplete configuration, it could produce a hard exit with the error like Sorry, could not locate bootstrap.inc. However, tracing this error was often difficult because the hard exit did not report a backtrace. This makes the error condition more debuggable.

Original Description

As discussed with @totten in the chat.

I'd like to fix that error_reporting call too but need some guidance first.

[totten]

jenkins, test this please

[eileenmcnaughton]

@totten can you look at this - I believe it is good-to-merge

[totten]

+1 @ErichBSchulz. I test a couple synthetic misconfigurations (e.g. missing bootstrap.inc and running loadBootStrap() by way of cv). This patch means that boot failures experienced in cv are easier to debug/inspect now. :)

[ErichBSchulz]

Cool! Hope it helps someone sometime