Compute worker: catch the case where metadata is empty

Dockerfile.compute_worker

@@ -1,4 +1,4 @@
-FROM python:3.8
+FROM --platform=linux/amd64 python:3.8
 
 # This makes output not buffer and return immediately, nice for seeing results in stdout
 ENV PYTHONUNBUFFERED 1

Dockerfile.compute_worker_gpu

@@ -1,13 +1,13 @@
-FROM python:3.8.1-buster
+FROM --platform=linux/amd64 python:3.8.1-buster
 
 # We need curl to get docker/nvidia-docker
 RUN apt-get update &&  apt-get install curl wget -y
 
 # This makes output not buffer and return immediately, nice for seeing results in stdout
 ENV PYTHONUNBUFFERED 1
 
-# Install a specific version of docker
-RUN curl -sSL https://get.docker.com/ | sed 's/docker-ce/docker-ce=18.03.0~ce-0~debian/' | sh
+# Install Docker
+RUN apt-get update && curl -fsSL https://get.docker.com | sh
 
 # nvidia-docker jazz
 RUN curl -s -L https://nvidia.github.io/nvidia-docker/gpgkey | apt-key add -

docker/compute_worker/compute_worker.py

@@ -484,7 +484,7 @@ async def _run_program_directory(self, program_dir, kind, can_be_output=False):
         with open(os.path.join(program_dir, metadata_path), 'r') as metadata_file:
             metadata = yaml.load(metadata_file.read(), Loader=yaml.FullLoader)
             logger.info(f"Metadata contains:\n {metadata}")
-            command = metadata.get("command")
+            command = metadata.get("command") if metadata is not None else None # in case the file exists but is empty
             if not command and kind == "ingestion":
                 raise SubmissionException("Program directory missing 'command' in metadata")
             elif not command: