use proper temp directories in test_tensorboard.py (#89826)

The old `temp_dir` is created under `PWD`. But `PWD` may not be writable and in general is not a good place to create temporary directories. Use the standard `tempfile` instead.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/89826
Approved by: https://github.com/soumith

test/test_tensorboard.py

@@ -5,8 +5,8 @@ import numpy as np
 import os
 import shutil
 import sys
+import tempfile
 import unittest
-import uuid
 import expecttest
 
 TEST_TENSORBOARD = True
@@ -60,7 +60,9 @@ class BaseTestCase(TestCase):
         self.temp_dirs = []
 
     def createSummaryWriter(self):
-        temp_dir = str(uuid.uuid4())
+        # Just to get the name of the directory in a writable place. tearDown()
+        # is responsible for clean-ups.
+        temp_dir = tempfile.TemporaryDirectory(prefix="test_tensorboard").name
         self.temp_dirs.append(temp_dir)
         return SummaryWriter(temp_dir)
 
@@ -287,11 +289,10 @@ class TestTensorBoardSummaryWriter(BaseTestCase):
 
     def test_pathlib(self):
         import pathlib
-        p = pathlib.Path('./pathlibtest' + str(uuid.uuid4()))
-        with SummaryWriter(p) as writer:
-            writer.add_scalar('test', 1)
-        import shutil
-        shutil.rmtree(str(p))
+        with tempfile.TemporaryDirectory(prefix="test_tensorboard_pathlib") as d:
+            p = pathlib.Path(d)
+            with SummaryWriter(p) as writer:
+                writer.add_scalar('test', 1)
 
 class TestTensorBoardEmbedding(BaseTestCase):
     def test_embedding(self):
@@ -516,7 +517,7 @@ def get_expected_file(function_ptr):
 
 def read_expected_content(function_ptr):
     expected_file = get_expected_file(function_ptr)
-    assert os.path.exists(expected_file)
+    assert os.path.exists(expected_file), expected_file
     with open(expected_file, "r") as f:
         return f.read()