Test that ValueError is raised when vfsopen is passed an invalid mode (#154008)

* ValueError with message test

* Remove white space

* Apply suggestions from code review

Change from double quotes to single quotes.

Co-authored-by: Tomas R. <tomas.roun8@gmail.com>

---------

Co-authored-by: Tomas R. <tomas.roun8@gmail.com>

Author: ravg998

Lib/test/test_pathlib/test_read.py

@@ -329,6 +329,11 @@ def test_info_is_symlink(self):
         self.assertFalse((p / 'fileA\udfff').info.is_symlink())
         self.assertFalse((p / 'fileA\x00').info.is_symlink())
 
+    def test_invalid_mode(self):
+        p = self.root / 'fileA'
+        with self.assertRaisesRegex(ValueError, 'invalid mode'):
+            vfsopen(p, 'q')
+
 
 class ZipPathReadTest(ReadTestBase, unittest.TestCase):
     ground = ZipPathGround(ReadableZipPath)