kunit: tool: use with open() in unit test

The use of manual open() and .close() calls seems to be an attempt to
keep the contents in scope.
But Python doesn't restrict variables like that, so we can introduce new
variables inside of a `with` and use them outside.

Do so to make the code more Pythonic.

Signed-off-by: Daniel Latypov <dlatypov@google.com>
Reviewed-by: David Gow <davidgow@google.com>
Tested-by: Brendan Higgins <brendanhiggins@google.com>
Acked-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Author: dlatypov

tools/testing/kunit/kunit_tool_test.py

@@ -100,15 +100,14 @@ def assertContains(self, needle, haystack):
 	def test_output_isolated_correctly(self):
 		log_path = get_absolute_path(
 			'test_data/test_output_isolated_correctly.log')
-		file = open(log_path)
-		result = kunit_parser.isolate_kunit_output(file.readlines())
+		with open(log_path) as file:
+			result = kunit_parser.isolate_kunit_output(file.readlines())
 		self.assertContains('TAP version 14', result)
 		self.assertContains('	# Subtest: example', result)
 		self.assertContains('	1..2', result)
 		self.assertContains('	ok 1 - example_simple_test', result)
 		self.assertContains('	ok 2 - example_mock_test', result)
 		self.assertContains('ok 1 - example', result)
-		file.close()
 
 	def test_output_with_prefix_isolated_correctly(self):
 		log_path = get_absolute_path(
@@ -143,55 +142,51 @@ def test_output_with_prefix_isolated_correctly(self):
 	def test_parse_successful_test_log(self):
 		all_passed_log = get_absolute_path(
 			'test_data/test_is_test_passed-all_passed.log')
-		file = open(all_passed_log)
-		result = kunit_parser.parse_run_tests(file.readlines())
+		with open(all_passed_log) as file:
+			result = kunit_parser.parse_run_tests(file.readlines())
 		self.assertEqual(
 			kunit_parser.TestStatus.SUCCESS,
 			result.status)
-		file.close()
 
 	def test_parse_failed_test_log(self):
 		failed_log = get_absolute_path(
 			'test_data/test_is_test_passed-failure.log')
-		file = open(failed_log)
-		result = kunit_parser.parse_run_tests(file.readlines())
+		with open(failed_log) as file:
+			result = kunit_parser.parse_run_tests(file.readlines())
 		self.assertEqual(
 			kunit_parser.TestStatus.FAILURE,
 			result.status)
-		file.close()
 
 	def test_no_tests(self):
 		empty_log = get_absolute_path(
 			'test_data/test_is_test_passed-no_tests_run.log')
-		file = open(empty_log)
-		result = kunit_parser.parse_run_tests(
-			kunit_parser.isolate_kunit_output(file.readlines()))
+		with open(empty_log) as file:
+			result = kunit_parser.parse_run_tests(
+				kunit_parser.isolate_kunit_output(file.readlines()))
 		self.assertEqual(0, len(result.suites))
 		self.assertEqual(
 			kunit_parser.TestStatus.NO_TESTS,
 			result.status)
-		file.close()
 
 	def test_no_kunit_output(self):
 		crash_log = get_absolute_path(
 			'test_data/test_insufficient_memory.log')
-		file = open(crash_log)
 		print_mock = mock.patch('builtins.print').start()
-		result = kunit_parser.parse_run_tests(
-			kunit_parser.isolate_kunit_output(file.readlines()))
+		with open(crash_log) as file:
+			result = kunit_parser.parse_run_tests(
+				kunit_parser.isolate_kunit_output(file.readlines()))
 		print_mock.assert_any_call(StrContains('no tests run!'))
 		print_mock.stop()
 		file.close()
 
 	def test_crashed_test(self):
 		crashed_log = get_absolute_path(
 			'test_data/test_is_test_passed-crash.log')
-		file = open(crashed_log)
-		result = kunit_parser.parse_run_tests(file.readlines())
+		with open(crashed_log) as file:
+			result = kunit_parser.parse_run_tests(file.readlines())
 		self.assertEqual(
 			kunit_parser.TestStatus.TEST_CRASHED,
 			result.status)
-		file.close()
 
 	def test_ignores_prefix_printk_time(self):
 		prefix_log = get_absolute_path(