Roofit upper limit unstable for negative pdf (with AsymptoticCalculator)

[StephanH]

@daritter

@StephanH you think it might be possible to update the nightlies page you linked to be a bit more explicit, also on how to use a python3 version by using dev3python3 instead of dev3 ?

Done! (… But a post must be at least 20 characters …)