Require command argument for br.py

If no command is provided, we end up with a syntactically invalid shell
script.

Author: larsks

br.py

@@ -186,6 +186,9 @@ def run(args: argparse.Namespace):
             "none": "dummy-localqueue",
         }
 
+        if not args.command:
+            sys.exit("ERROR: you must provide a command")
+
         if args.gpu not in DEFAULT_QUEUES:
             sys.exit(f"ERROR: unsupported GPU {args.gpu} : no queue found")
         queue_name = DEFAULT_QUEUES[args.gpu]

tests/test_br.py

@@ -16,6 +16,7 @@ def tempdir():
 
 def test_invalid_gpu(args: argparse.Namespace):
     args.gpu = "invalid"
+    args.command = ["true"]
     with pytest.raises(SystemExit) as err:
         CreateJobCommand.run(args)
 
@@ -40,6 +41,7 @@ def test_create_job_nowait(
     args = parser.parse_args(["br"])
     args.wait = False
     args.job_id = 123
+    args.command = ["true"]
 
     mock_getcwd.return_value = tempdir
     mock_gethostname.return_value = "testhost"