Raise on failed docker build

build.py

@@ -146,7 +146,10 @@ def docker_buildx(repository: str, tags: list[str], build_platforms: list[Docker
                *[t for label in labels for t in ("--tag", label)],
                "--pull", "--push", directory]
     print(" ".join(command))
-    subprocess.run(command)
+    process = subprocess.run(command, stderr=subprocess.PIPE)
+    if process.returncode != 0:
+        error = process.stderr.decode('utf-8')
+        raise Exception(error)
 
 
 default_java_version: JavaVersion = {