Try `/` rather than ` `

ci/delete_old_binaries.py

@@ -11,7 +11,7 @@ def main():
     days_to_keep = int(sys.argv[2])
     print(f"Looking for binaries to delete older than {days_to_keep} days")
 
-    files_lines = execute_cli(f"b2 ls --long --versions {bucket} nightly").split("\n")
+    files_lines = execute_cli(f"b2 ls --long --versions {bucket}/nightly").split("\n")
     print(files_lines)
     for x in files_lines:
         parts = [y for y in x.split(' ') if y]