Feature Request: Clearer error message when unable to connect to docker

TLDR: Add exception handlers on docker/tranport/unixconn.py to print user friendly error message that docker daemon is unreachable.

Description

I set up a fresh install of docker on a new Apple Macbook (running Apple Silicon). When I ran docker-compose up, I got a cryptic error message. Further investigation showed that the docker daemon was not running. However, the error messages are very arcane and a junior dev would not have known what the issue is.

Proposed fix: Instead of printing docker transport stack traces, provide user friendly notification asking user to verify docker is running.

Steps to reproduce the issue:

1. Install docker on apple macbook, using factory settings
2. reboot machine, so that docker daemon is off
3. Run docker compose, observe cryptic stack trace:

Describe the results you received:

Stack trace:

docker-compose -f docker/docker-compose.yml up --build
Traceback (most recent call last):
  File "urllib3/connectionpool.py", line 670, in urlopen
  File "urllib3/connectionpool.py", line 392, in _make_request
  File "http/client.py", line 1255, in request
  File "http/client.py", line 1301, in _send_request
  File "http/client.py", line 1250, in endheaders
  File "http/client.py", line 1010, in _send_output
  File "http/client.py", line 950, in send
  File "docker/transport/unixconn.py", line 43, in connect
FileNotFoundError: [Errno 2] No such file or directory

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "requests/adapters.py", line 439, in send
  File "urllib3/connectionpool.py", line 726, in urlopen
  File "urllib3/util/retry.py", line 410, in increment
  File "urllib3/packages/six.py", line 734, in reraise
  File "urllib3/connectionpool.py", line 670, in urlopen
  File "urllib3/connectionpool.py", line 392, in _make_request
  File "http/client.py", line 1255, in request
  File "http/client.py", line 1301, in _send_request
  File "http/client.py", line 1250, in endheaders
  File "http/client.py", line 1010, in _send_output
  File "http/client.py", line 950, in send
  File "docker/transport/unixconn.py", line 43, in connect
urllib3.exceptions.ProtocolError: ('Connection aborted.', FileNotFoundError(2, 'No such file or directory'))

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/utils/decorators.py", line 46, in inner
  File "docker/api/client.py", line 237, in _get
  File "requests/sessions.py", line 543, in get
  File "requests/sessions.py", line 530, in request
  File "requests/sessions.py", line 643, in send
  File "requests/adapters.py", line 498, in send
requests.exceptions.ConnectionError: ('Connection aborted.', FileNotFoundError(2, 'No such file or directory'))

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: ('Connection aborted.', FileNotFoundError(2, 'No such file or directory'))
[23301] Failed to execute script docker-compose

Describe the results you expected:

As we can see, we get multiple stack traces from docker. Luckily, someone with networking knowledge can realize that the key parts are docker.errors.DockerException: Error while fetching server API version: ('Connection aborted.' and docker/transport/unixconn.py", line 43, in connect, thus leading the user to check the docker connection status. However, this is not at all intuitive.

It would be much better to have a try/except block that can catch these errors, then run a quick ping check on the docker socket and print a friendly user messages saying "Docker is unreachable, please verify docker service is running and accessible on $docker_conn_socket, where $docker_conn_socket is whatever is specified in the daemon.

Additional information you deem important (e.g. issue happens only occasionally):
This will disproportionally impact new users of docker who are junior devs. We should make this more friendly to them.

Output of docker compose version:

Docker Compose version v2.0.0

Output of docker info:

Factory settings on Apple Silicon:

Client:
 Context:    default
 Debug Mode: false
 Plugins:
  buildx: Build with BuildKit (Docker Inc., v0.6.3)
  compose: Docker Compose (Docker Inc., v2.0.0)
  scan: Docker Scan (Docker Inc., v0.8.0)

Server:
 Containers: 2
  Running: 0
  Paused: 0
  Stopped: 2
 Images: 9
 Server Version: 20.10.8
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Native Overlay Diff: true
  userxattr: false
 Logging Driver: json-file
 Cgroup Driver: cgroupfs
 Cgroup Version: 1
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
 Swarm: inactive
 Runtimes: io.containerd.runc.v2 io.containerd.runtime.v1.linux runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: e25210fe30a0a703442421b0f60afac609f950a3
 runc version: v1.0.1-0-g4144b63
 init version: de40ad0
 Security Options:
  seccomp
   Profile: default
 Kernel Version: 5.10.47-linuxkit
 Operating System: Docker Desktop
 OSType: linux
 Architecture: aarch64
 CPUs: 5
 Total Memory: 1.942GiB
 Name: docker-desktop
 ID: PRTC:U5RD:K2GE:N7A4:346H:SFMO:LB7O:KWRS:Q6HC:NB3F:JTCV:C3XT
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 HTTP Proxy: http.docker.internal:3128
 HTTPS Proxy: http.docker.internal:3128
 Registry: https://index.docker.io/v1/
 Labels:
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Live Restore Enabled: false

Additional environment details:
N/A, this is a docker internal issue.

Start in docker/transport/unixconn.py and trace how the docker-compose command reaches the Docker client when the Unix socket is unavailable. Reproduce the failure with docker-compose -f docker/docker-compose.yml up --build; done means the cryptic stack traces are replaced with a friendly unreachable-daemon message that identifies the configured socket.