Use subprocess.check_output in tests (#5465)

python/ray/tests/test_monitors.py

@@ -10,18 +10,19 @@ import time
 
 import ray
 
-from ray.tests.utils import run_and_get_output
-
 
 def _test_cleanup_on_driver_exit(num_redis_shards):
-    stdout = run_and_get_output([
-        "ray",
-        "start",
-        "--head",
-        "--num-redis-shards",
-        str(num_redis_shards),
-    ])
-    lines = [m.strip() for m in stdout.split("\n")]
+    output = ray.utils.decode(
+        subprocess.check_output(
+            [
+                "ray",
+                "start",
+                "--head",
+                "--num-redis-shards",
+                str(num_redis_shards),
+            ],
+            stderr=subprocess.STDOUT))
+    lines = [m.strip() for m in output.split("\n")]
     init_cmd = [m for m in lines if m.startswith("ray.init")]
     assert 1 == len(init_cmd)
     redis_address = init_cmd[0].split("redis_address=\"")[-1][:-2]
@@ -90,7 +91,7 @@ def _test_cleanup_on_driver_exit(num_redis_shards):
     assert (0, 1) == StateSummary()
 
     ray.shutdown()
-    subprocess.Popen(["ray", "stop"]).wait()
+    subprocess.check_output(["ray", "stop"])
 
 
 @pytest.mark.skipif(