No error message if sonar.cxx.xunit.xsltURL file does not exist

[guwirth]

If file defined with sonar.cxx.xunit.xsltURL is not available or can't be read there is no error message.
=> analysis breaks without any hint.

[wenns]

Ok. Looks like a good opportunity to try Behavior Driven Development on sonar-cxx (write failing scenario and then change production code) ;)

[guwirth]

Good idea. Only not sure what the default behavior should be in such a case:
(1) Create an error message and break analysis.
(2) Create an error message and continue analysis.
I tend to (1) because configuration is wrong, please vote.

[wenns]

I'm for 1). This is basically status quo + additional logging.