[LNT, NFC] Open tmp file in a context

Summary:
Simplify opening tmp file by using a context to have automatic closing
of the file descriptor.

Reviewers: cmatthews, hubert.reinterpretcast, leandron, PrzemekWirkus, kristof.beyls

Reviewed By: PrzemekWirkus

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D71058

Author: Thomas Preud'homme

lnt/util/ImportData.py

@@ -338,9 +338,8 @@ def import_from_string(config, db_name, db, session, ts_name, data,
     prefix = utcnow.strftime("data-%Y-%m-%d_%H-%M-%S")
     fd, path = tempfile.mkstemp(prefix=prefix, suffix='.json',
                                 dir=str(tmpdir), text=True)
-    fp = os.fdopen(fd, "w")
-    fp.write(data)
-    fp.close()
+    with os.fdopen(fd, "w") as fp:
+        fp.write(data)
 
     # Import the data.
     #