Request for "classic" confinement for package Wilfred

I can’t get it to work, the snap package isn’t able to speak to the Docker socket. Does docker have to be installed via snap (because right now I have Docker installed separately)?

  File "/snap/wilfred/x1/lib/python3.6/site-packages/docker/transport/unixconn.py", line 43, in connect
    sock.connect(self.unix_socket)
PermissionError: [Errno 13] Permission denied

This is my snapcraft.yaml.

name: wilfred
base: core18
version: git # set version on release ('0.1.0') and use 'git' during dev
summary: A CLI for managing game servers using Docker # 79 char long summary
description: |
  Wilfred is a command-line interface for running game servers locally. It uses Docker to run game servers in containers, which means they are completely separated. Wilfred can run any game that can run in Docker.

  Wilfred is currently under development and should not be considered stable. Features may brake or may not be implemented yet. Use with caution.

grade: stable # 'stable' on release ('devel' during dev)
confinement: strict

plugs:
  docker:
    content: docker
    default-provider: docker
    interface: content
    target: docker-env
  network:

parts:
  wilfred:
    plugin: python
    source: .
    build-packages:
      - python3-distutils
      - build-essential
    stage-packages:
      - python3-distutils
      - build-essential

apps:
  wilfred:
    command: bin/wilfred
    plugs: [docker, network]
    environment:
      PYTHONIOENCODING: utf-8
      LC_ALL: C.UTF-8
      LANG: C.UTF-8