Fail or warn when module isn't found?

Right now if a module isn't found, we exit 1 and fail. Output looks like this:

Checking for duplicate modules ...

tilelive was not found in the node_modules tree

Alternatively, we could just print a warning since this isn't necessarily a bad thing, it just means the module isn't being installed (presumably because it's not longer being used). Output could instead look like:

Checking for duplicate modules ...

✔ @mapbox/vtquery has only one version
? tilelive was not found in the node_modules tree

cc @mapbox/core-tech

No se indica ningún archivo, prueba ni punto de entrada. Empieza localizando el código que gestiona un módulo ausente en el árbol de node_modules y revisa cómo se prueban su estado de salida y su salida. Se considera terminado cuando el proyecto tiene un comportamiento fail-or-warn decidido, una salida coincidente y cobertura para el caso del módulo ausente.