Prefix the container hash with sha256:

The new docker version no longers supports building from just the hash, it must
be prefixed with sha256: or the image will not be found.

pytest_container/container.py

@@ -647,7 +647,7 @@ def __post_init__(self) -> None:
 
     def __str__(self) -> str:
         return (
-            self.container_id
+            f"sha256:{self.container_id}"
             or f"container derived from {self.base.__str__()}"
         )
 
@@ -690,7 +690,7 @@ def prepare_container(
                     self.base
                     if isinstance(self.base, str)
                     else getattr(self.base, "url", self.base.container_id)
-                    or self.base.container_id
+                    or f"sha256:{self.base.container_id}"
                 )
                 assert from_id
                 containerfile_contents = f"""FROM {from_id}

tests/test_inspect.py

@@ -32,7 +32,7 @@ def test_inspect(container: ContainerData):
     assert (
         "HOME" in inspect.config.env and inspect.config.env["HOME"] == "/src/"
     )
-    assert inspect.config.image == str(container.container)
+    assert f"sha256:{inspect.config.image}" == str(container.container)
     assert inspect.config.cmd == ["/bin/sh"]
 
     assert (