update prepare script

scripts/prepare_singularity.py

 #!/usr/bin/python3
 import os
 import sys
-import classad
+import json
 
 
 def get_job_ad():
     instream = sys.stdin
-    try:
-        job_ad = classad.parseOne(instream, parser=classad.Parser.Auto)
-    except (SyntaxError, ValueError) as e:
-        print(f"Failed to parse ClassAd: {e}")
-        return None
+    job_ad = {}
+    # format of the job ad is key = value
+    for line in instream:
+        if "=" in line:
+            key, value = line.split(" = ")
+            job_ad[key.strip()] = value.strip()
     return job_ad
 
 
@@ -49,6 +50,10 @@ def check_image_availability(image_path):
 
 def main():
     job_ad = get_job_ad()
+    # write job_ad to a json file for debugging
+    dumpfilepath = "/scratch/job_ad.json"
+    with open(dumpfilepath, "w") as f:
+        json.dump(job_ad, f, indent=4)
     container_image = job_ad.get("container_image")
     docker_image = job_ad.get("docker_image")