`unix://` client URL fails

[AstraLuma]

Doing #3146 (comment) , and I'm now getting errors like:

  File "/home/astraluma/code/unholy/unholy/docker.py", line 48, in get_client
    return docker.DockerClient(
           ^^^^^^^^^^^^^^^^^^^^
  File "/home/astraluma/.local/pipx/venvs/unholy/lib/python3.12/site-packages/docker/client.py", line 45, in __init__
    self.api = APIClient(*args, **kwargs)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/astraluma/.local/pipx/venvs/unholy/lib/python3.12/site-packages/docker/api/client.py", line 197, in __init__
    self._version = self._retrieve_server_version()
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/astraluma/.local/pipx/venvs/unholy/lib/python3.12/site-packages/docker/api/client.py", line 221, in _retrieve_server_version
    raise DockerException(
docker.errors.DockerException: Error while fetching server API version: Not supported URL scheme http+docker

The initial root looks like:

docker-py/docker/api/client.py

Line 153 in 03e43be

if base_url.startswith('http+unix://'):

where it looks for http+unix:// but not unix://.

But if I munge the URL to be http+unix:// instead, I get:

Traceback (most recent call last):
  File "/home/astraluma/.local/pipx/venvs/unholy/lib/python3.12/site-packages/requests/adapters.py", line 633, in send
    conn = self.get_connection_with_tls_context(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/astraluma/.local/pipx/venvs/unholy/lib/python3.12/site-packages/requests/adapters.py", line 489, in get_connection_with_tls_context
    conn = self.poolmanager.connection_from_host(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/astraluma/.local/pipx/venvs/unholy/lib/python3.12/site-packages/urllib3/poolmanager.py", line 303, in connection_from_host
    return self.connection_from_context(request_context)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/astraluma/.local/pipx/venvs/unholy/lib/python3.12/site-packages/urllib3/poolmanager.py", line 325, in connection_from_context
    raise URLSchemeUnknown(scheme)
urllib3.exceptions.URLSchemeUnknown: Not supported URL scheme http+docker

Note that the Docker CLI is fine with unix://.

[AstraLuma]

$ docker context ls
NAME        DESCRIPTION                               DOCKER ENDPOINT                            ERROR
default *   Current DOCKER_HOST based configuration   unix:///run/user/1000/podman/podman.sock   
docker      system docker                             unix:///var/run/docker.sock                
podman      user podman                               unix:///run/user/1000/podman/podman.sock   
Warning: DOCKER_HOST environment variable overrides the active context. To use a context, either set the global --context flag, or unset DOCKER_HOST environment variable.
$ docker -c podman version
Client: Docker Engine - Community
 Version:           27.4.0
 API version:       1.41 (downgraded from 1.47)
 Go version:        go1.22.10
 Git commit:        bde2b89
 Built:             Sat Dec  7 10:39:01 2024
 OS/Arch:           linux/amd64
 Context:           podman

Server: linux/amd64/debian-unknown
 Podman Engine:
  Version:          5.3.1
  APIVersion:       5.3.1
  Arch:             amd64
  BuildTime:        2024-12-06T08:13:07-05:00
  Experimental:     false
  GitCommit:        
  GoVersion:        go1.23.4
  KernelVersion:    6.11.9-amd64
  MinAPIVersion:    4.0.0
  Os:               linux
 Conmon:
  Version:          conmon version 2.1.12, commit: unknown
  Package:          conmon_2.1.12-3_amd64
 OCI Runtime (crun):
  Version:          crun version 1.18.2
commit: 00ab38af875ddd0d1a8226addda52e1de18339b5
rundir: /run/user/1000/crun
spec: 1.0.0
+SYSTEMD +SELINUX +APPARMOR +CAP +SECCOMP +EBPF +WASM:wasmedge +YAJL
  Package:          crun_1.18.2-1_amd64
 Engine:
  Version:          5.3.1
  API version:      1.41 (minimum version 1.24)
  Go version:       go1.23.4
  Git commit:       
  Built:            Fri Dec  6 08:13:07 2024
  OS/Arch:          linux/amd64
  Experimental:     false
$ docker -c docker version
Client: Docker Engine - Community
 Version:           27.4.0
 API version:       1.47
 Go version:        go1.22.10
 Git commit:        bde2b89
 Built:             Sat Dec  7 10:39:01 2024
 OS/Arch:           linux/amd64
 Context:           docker

Server: Docker Engine - Community
 Engine:
  Version:          27.4.0
  API version:      1.47 (minimum version 1.24)
  Go version:       go1.22.10
  Git commit:       92a8393
  Built:            Sat Dec  7 10:39:01 2024
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.7.24
  GitCommit:        88bf19b2105c8b17560993bee28a01ddc2f97182
 runc:
  Version:          1.2.2
  GitCommit:        v1.2.2-0-g7cb3632
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0