[1.6.x] Created import-time test temp dirs in known location

Refs #17215. In the same spirit as 5de31cb8cb.
Backport of 809362518d from master.

tests/bug639/models.py

@@ -1,3 +1,4 @@
+import os
 import tempfile
 
 from django.core.files.storage import FileSystemStorage
@@ -5,7 +6,7 @@ from django.db import models
 from django.forms import ModelForm
 
 
-temp_storage_dir = tempfile.mkdtemp()
+temp_storage_dir = tempfile.mkdtemp(dir=os.environ['DJANGO_TEST_TEMP_DIR'])
 temp_storage = FileSystemStorage(temp_storage_dir)
 
 class Photo(models.Model):

tests/file_uploads/tests.py

@@ -23,7 +23,7 @@ from .models import FileModel
 
 
 UNICODE_FILENAME = 'test-0123456789_中文_Orléans.jpg'
-MEDIA_ROOT = sys_tempfile.mkdtemp()
+MEDIA_ROOT = sys_tempfile.mkdtemp(dir=os.environ['DJANGO_TEST_TEMP_DIR'])
 UPLOAD_TO = os.path.join(MEDIA_ROOT, 'test_upload')
 
 @override_settings(MEDIA_ROOT=MEDIA_ROOT)

tests/model_fields/models.py

@@ -132,7 +132,7 @@ if Image:
         attr_class = TestImageFieldFile
 
     # Set up a temp directory for file storage.
-    temp_storage_dir = tempfile.mkdtemp()
+    temp_storage_dir = tempfile.mkdtemp(dir=os.environ['DJANGO_TEST_TEMP_DIR'])
     temp_storage = FileSystemStorage(temp_storage_dir)
     temp_upload_to_dir = os.path.join(temp_storage.location, 'tests')