[DRE-maint] Bug#1100010: schleuder: API daemon fails: undefined method `register' for module Rack::Handler (NoMethodError)

[Gabriel Filion]

Hello,

I'm able to reproduce this bug on testing by just installing the 
schleuder package.

Once that's done we can see that schleuder-api-daemon.service is 
erroring out on startup

I'm not very confident about my skills for analysing ruby errors.. but 
it looks like the problem might be stemming from ruby-rackup. it was 
added to the dependency list on jan 31st and migrated to testing only on 
february 12th.