Fix some tests

Author: slozier

tests/IronPython.Tests/Cases/CPythonCasesManifest.ini

@@ -186,6 +186,9 @@ Ignore=true
 Ignore=true
 Reason=ImportError: No module named audioop
 
+[CPython.test_base64]
+IsolationLevel=PROCESS # https://github.com/IronLanguages/ironpython3/issues/1440
+
 [CPython.test_bdb] # new in 3.6
 Ignore=true
 

tests/suite/test_file.py

@@ -688,7 +688,7 @@ def test_errors(self):
 
         with self.assertRaises(OSError) as cm:
             open('path_too_long' * 100)
-        self.assertEqual(cm.exception.errno, (errno.ENAMETOOLONG if is_posix else errno.EINVAL) if is_netcoreapp or sys.version_info >= (3,6) else errno.ENOENT)
+        self.assertEqual(cm.exception.errno, (errno.ENAMETOOLONG if is_posix else errno.EINVAL) if is_netcoreapp or is_cpython and sys.version_info >= (3,6) else errno.ENOENT)
 
     def test_write_bytes(self):
         fname = self.temp_file

tests/suite/test_threading_stdlib.py

@@ -14,7 +14,16 @@ def load_tests(loader, standard_tests, pattern):
     tests = loader.loadTestsFromModule(test.test_threading)
 
     if is_ironpython:
-        failing_tests = []
+        failing_tests = [
+            test.test_threading.CRLockTests('test_weakref_deleted'), # TypeError: cannot create weak reference to 'RLock' object
+            test.test_threading.CRLockTests('test_weakref_exists'), # TypeError: cannot create weak reference to 'RLock' object
+            test.test_threading.LockTests('test_weakref_deleted'), # TypeError: cannot create weak reference to 'lock' object
+            test.test_threading.LockTests('test_weakref_exists'), # TypeError: cannot create weak reference to 'lock' object
+            test.test_threading.ConditionAsRLockTests('test_weakref_deleted'), # AssertionError
+            test.test_threading.PyRLockTests('test_weakref_deleted'), # AssertionError
+            test.test_threading.ThreadTests('test_main_thread_during_shutdown'), # AssertionError
+            test.test_threading.ThreadingExceptionTests('test_bare_raise_in_brand_new_thread'), # AssertionError: TypeError('exceptions must derive from BaseException',) is not an instance of <class 'RuntimeError'>
+        ]
 
         skip_tests = [
             test.test_threading.SubinterpThreadingTests('test_threads_join'), # ImportError: No module named '_testcapi'