Integration test relative-script-snapshots is failing

[qrilka]

Running integration tests for #4409 I've found that relative-script-snapshots fails and the same happens on the current master, it looks like something which could have appeared in #4593

[qrilka]

And script-extra-dep fails in a similar way:

       stderr:
       Running: /home/qrilka/ws/h/stack/.stack-work/install/x86_64-linux-tinfo6/custom-snapshot-for-building-stack-with-ghc-8.2.2-RcJFh0uLBqbP/8.2.2/bin/stack script.hs
       Assertion failed
       CallStack (from HasCallStack):
         assert, called at src/Stack/Script.hs:100:26 in stack-1.10.0-1nLeFC5kSCGKBAYoZ1mLri:Stack.Script
       Main.hs: Exited with exit code: ExitFailure 1