Print only part of a stack trace

[Dennis]

On assertion failure, the default error handler prints a stack 
trace that looks like this

[library functions]
[application functions]
[druntime start-up functions]

I'm only interested in application functions, the rest is noise.
I could easily filter unwanted lines out if I had the stack trace 
in string form, but I don't know how to obtain that. Is there a 
simple way to do this, or should I delve into Druntime internals?