Support Podman for mocking Lambda (#3702)

* Support Podman for mocking Lambda

Podman supports all Docker APIs used in moto since version 3.0. Note
that Podman requires pulling the image before creating a container
using a fully-qualified image name (e.g., "docker.io/library/busybox"
instead of "busybox").

Test plan:
$ podman system service -t 0
$ DOCKER_HOST="unix://$XDG_RUNTIME_DIR/podman/podman.sock" pytest

Fixes https://github.com/spulec/moto/issues/3276

* Run black

* Python 2 compatibility

* Address review comments and improve parse_image_ref

moto/utilities/docker_utilities.py

@@ -2,6 +2,8 @@ import docker
 import functools
 import requests.adapters
 
+from moto import settings
+
 
 _orig_adapter_send = requests.adapters.HTTPAdapter.send
 
@@ -31,3 +33,27 @@ class DockerModel:
 
                 self.docker_client.api.get_adapter = replace_adapter_send
         return self.__docker_client
+
+
+def parse_image_ref(image_name):
+    # podman does not support short container image name out of box - try to make a full name
+    # See ParseDockerRef() in https://github.com/distribution/distribution/blob/main/reference/normalize.go
+    parts = image_name.split("/")
+    if len(parts) == 1 or (
+        "." not in parts[0] and ":" not in parts[0] and parts[0] != "localhost"
+    ):
+        domain = settings.DEFAULT_CONTAINER_REGISTRY
+        remainder = parts
+    else:
+        domain = parts[0]
+        remainder = parts[1:]
+    # Special handling for docker.io
+    # https://github.com/containers/image/blob/master/docs/containers-registries.conf.5.md#normalization-of-dockerio-references
+    if domain == "docker.io" and len(remainder) == 1:
+        remainder = ["library"] + remainder
+    if ":" in remainder[-1]:
+        remainder[-1], image_tag = remainder[-1].split(":", 1)
+    else:
+        image_tag = "latest"
+    image_repository = "/".join([domain] + remainder)
+    return image_repository, image_tag