fix error when mc admin response has a trailing newline (#1099)

To avoid empty strings after splitting `proc.stdout`, `splitlines` is used
instead of `split`.

To avoid errors when `proc.stdout` itself is empty, an additional guard has been
added. In this case, an empty list or dictionary is returned, depending on
`multiline`.

Also, `text=True` is passed `subprocess.run` to ensure `proc.stdout` is a string
and not bytes object.

minio/minioadmin.py

@@ -48,9 +48,12 @@ def _run(self, args, multiline=False):
             capture_output=True,
             timeout=self._timeout,
             check=True,
+            text=True,
         )
+        if not proc.stdout:
+            return [] if multiline else {}
         if multiline:
-            return [json.loads(line) for line in proc.stdout.split("\n")]
+            return [json.loads(line) for line in proc.stdout.splitlines()]
         return json.loads(proc.stdout)
 
     def service_restart(self):