Dentro de mi docker-compose.yml estoy usando el contexto de la dirección ssh para construir una imagen de Docker.

 ui: build: context: git@my.git.host:ui/ui.git dockerfile: Dockerfile.prod container_name: ui ports: - "4200:4200" command: ember serve

Ejecutar docker-compose build ui me da:

 compose.cli.verbose_proxy.proxy_callable: docker build -> <generator object APIClient._stream_helper at 0x7faa8bc107d8> ERROR: compose.cli.errors.log_api_error: error fetching: Host key verification failed. fatal: Could not read from remote repository. Please make sure you have the correct access rights and the repository exists.

Si construyo la imagen usando docker build, funciona normalmente

docker build git@my.git.host:ui/ui.git -f Dockerfile.prod

mi contexto

 compose.cli.command.get_client: docker-compose version 1.21.0, build unknown docker-py version: 4.0.1 CPython version: 3.6.7 OpenSSL version: OpenSSL 1.1.1 11 Sep 2018

EDICIÓN POSTERIOR:
Logré reproducir el problema usando el docker pip

 import docker client = docker.APIClient() log = client.build(path="git@my.git.host:ui/ui.git", dockerfile="Dockerfile.prod") for chunk in log: print(loc)

Producción:

 docker.errors.APIError: 500 Server Error: Internal Server Error ("error fetching: Host key verification failed. fatal: Could not read from remote repository. Please make sure you have the correct access rights and the repository exists. : exit status 128")