【docker-compose】requests.exceptions.HTTPError: 500 Server Error: Internal Server Error for url: http+docker://localhost/version

エラー内容

下記の記事を参考に
https://qiita.com/eighty8/items/0288ab9c127ddb683315

$ docker-compose run --rm app rails new . --force --database=mysql --skip-bundle

を入力したところ、下記のエラーが発生。

Traceback (most recent call last):
  File "docker/api/client.py", line 268, in _raise_for_status
  File "requests/models.py", line 941, in raise_for_status
requests.exceptions.HTTPError: 500 Server Error: Internal Server Error for url: http+docker://localhost/version

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "docker/api/client.py", line 214, in _retrieve_server_version
  File "docker/api/daemon.py", line 181, in version
  File "docker/api/client.py", line 274, in _result
  File "docker/api/client.py", line 270, in _raise_for_status
  File "docker/errors.py", line 31, in create_api_error_from_http_exception
docker.errors.APIError: 500 Server Error for http+docker://localhost/version: Internal Server Error ("b'dial unix docker.raw.sock: connect: connection refused'")

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "docker-compose", line 3, in <module>
  File "compose/cli/main.py", line 81, in main
  File "compose/cli/main.py", line 200, in perform_command
  File "compose/cli/command.py", line 60, in project_from_options
  File "compose/cli/command.py", line 152, in get_project
  File "compose/cli/docker_client.py", line 41, in get_client
  File "compose/cli/docker_client.py", line 170, in docker_client
  File "docker/api/client.py", line 197, in __init__
  File "docker/api/client.py", line 221, in _retrieve_server_version
docker.errors.DockerException: Error while fetching server API version: 500 Server Error for http+docker://localhost/version: Internal Server Error ("b'dial unix docker.raw.sock: connect: connection refused'")
[6004] Failed to execute script docker-compose

解決策

こちらの記事を参考に、
https://github.com/docker/for-win/issues/9561
docker-compose.ymlのversion指定をシングルクォーテーションからダブルクォーテーションに変えたらエラーが消えました。

# 修正前
version: '3'

# 修正後
version: "3"

理由はわかりません。