reproduce https://github.com/neomake/neomake/issues/2411

docker-compose.yml

version: '3'
services:
  web:
    image: ruby:2.5.3
    tty: true
    stdin_open: true
    command: bash -c "bundle && irb"
    volumes:
      - .:/app
      - /tmp/:/tmp
    working_dir: /app

Gemfile

source "https://rubygems.org"

gem "rubocop", :require => false

test.rb

STR = "abc"