docker-compose up -d fails at Step 9/17 : RUN bundle install

[C-Fu]

# docker-compose up -d
WARNING: The RAILS_ENV variable is not set. Defaulting to a blank string.
Building sidekiq
Sending build context to Docker daemon  23.85MB

Step 1/17 : FROM ruby:2.3.7
 ---> 205d0fa463d7
Step 2/17 : RUN mkdir -p /usr/src/osb
 ---> Using cache
 ---> 8c01626ad02c
Step 3/17 : RUN apt-get update && apt-get install -y nodejs --no-install-recommends && rm -rf /var/lib/apt/lists/*
 ---> Using cache
 ---> fd9047762f27
Step 4/17 : RUN gem install bundler --no-document
 ---> Using cache
 ---> 6da2e595a287
Step 5/17 : WORKDIR /usr/src/osb
 ---> Using cache
 ---> 15b3861f9860
Step 6/17 : COPY Gemfile* /usr/src/osb/
 ---> Using cache
 ---> 363bc310de4b
Step 7/17 : COPY Gemfile Gemfile.lock ./
 ---> Using cache
 ---> 3bba88d0eb61
Step 8/17 : COPY vendor/engines ./vendor/engines/
 ---> 22bb67a46230
Step 9/17 : RUN bundle install
 ---> Running in 50ef8442715e
You must use Bundler 2 or greater with this lockfile.
The command '/bin/sh -c bundle install' returned a non-zero code: 20
ERROR: Service 'sidekiq' failed to build

[Gibbo3771]

Change the docker version for ruby to 2.7.1. I also suggest you fork this repo and fix the problem yourself. PR #104 fixes this but it's been open for over a year+ so this repo is basically dead.

EDIT: Also the docker is not even remotely setup to be useful. Points to the wrong hosts and everything.