Use --iidfile & --cidfile to get the ctr & img ids

We don't have to rely on stdout containing the img id, which is not the case
with the newest docker.

pytest_container/container.py

@@ -33,6 +33,7 @@
 from typing import overload
 from typing import Type
 from typing import Union
+from uuid import uuid4
 
 import pytest
 import testinfra
@@ -682,6 +683,7 @@ def prepare_container(
 
         with tempfile.TemporaryDirectory() as tmpdirname:
             containerfile_path = os.path.join(tmpdirname, "Dockerfile")
+            iidfile = os.path.join(tmpdirname, str(uuid4()))
             with open(containerfile_path, "w") as containerfile:
                 from_id = (
                     self.base
@@ -747,12 +749,22 @@ def prepare_container(
                     if self.add_build_tags
                     else []
                 )
-                + ["-f", containerfile_path, str(rootdir)]
+                + [
+                    f"--iidfile={iidfile}",
+                    "-f",
+                    containerfile_path,
+                    str(rootdir),
+                ]
             )
+
             _logger.debug("Building image via: %s", cmd)
-            self.container_id = runtime.get_image_id_from_stdout(
-                check_output(cmd).decode().strip()
-            )
+            check_output(cmd)
+
+            with open(iidfile, "r") as iidfile_f:
+                hash, img_id = iidfile_f.read(-1).strip().split(":")
+                assert hash == "sha256"
+                self.container_id = img_id
+
             _logger.debug(
                 "Successfully build the container image %s", self.container_id
             )
@@ -862,6 +874,12 @@ class ContainerLauncher:
 
     _stack: contextlib.ExitStack = field(default_factory=contextlib.ExitStack)
 
+    _cidfile: str = field(
+        default_factory=lambda: os.path.join(
+            tempfile.gettempdir(), str(uuid4())
+        )
+    )
+
     def __enter__(self) -> "ContainerLauncher":
         return self
 
@@ -918,6 +936,8 @@ def release_lock() -> None:
         if self.container_name:
             extra_run_args.extend(["--name", self.container_name])
 
+        extra_run_args.append(f"--cidfile={self._cidfile}")
+
         # We must perform the launches in separate branches, as containers with
         # port forwards must be launched while the lock is being held. Otherwise
         # another container could pick the same ports before this one launches.
@@ -934,14 +954,17 @@ def release_lock() -> None:
                 )
 
                 _logger.debug("Launching container via: %s", launch_cmd)
-                self._container_id = check_output(launch_cmd).decode().strip()
+                check_output(launch_cmd)
         else:
             launch_cmd = self.container.get_launch_cmd(
                 self.container_runtime, extra_run_args=extra_run_args
             )
 
             _logger.debug("Launching container via: %s", launch_cmd)
-            self._container_id = check_output(launch_cmd).decode().strip()
+            check_output(launch_cmd)
+
+        with open(self._cidfile, "r") as cidfile:
+            self._container_id = cidfile.read(-1).strip()
 
         self._wait_for_container_to_become_healthy()