More Appveyor fixes

Plus a PyPy fix, now that the tests are running again.

src/gevent/libev/corecffi.py

@@ -56,7 +56,12 @@ class _Callbacks(AbstractCallbacks):
     # pylint:disable=arguments-differ,arguments-renamed
 
     def python_check_callback(self, *args):
-        pass
+        # There's a pylint bug (pylint 2.9.3, astroid 2.6.2) that causes pylint to crash
+        # with an AttributeError on certain types of arguments-differ errors
+        # But code in _ffi/loop depends on being able to find the watcher_ptr
+        # argument is the local frame.
+        # pylint:disable=unused-variable
+        _loop, watcher_ptr, _events = args
 
     def python_prepare_callback(self, _loop_ptr, watcher_ptr, _events):
         AbstractCallbacks.python_prepare_callback(self, watcher_ptr)

src/gevent/testing/patched_tests_setup.py

@@ -1352,6 +1352,8 @@ if PY39:
             'test_httplib.BasicTest.test_dir_with_added_behavior_on_status',
             'test_httplib.TunnelTests.test_tunnel_connect_single_send_connection_setup',
             'test_ssl.TestSSLDebug.test_msg_callback_deadlock_bpo43577',
+            # This one fails with the updated certs
+            'test_ssl.ContextTests.test_load_verify_cadata',
             # This one times out on 3.7.1 on Appveyor
             'test_ftplib.TestTLS_FTPClassMixin.test_retrbinary_rest',
         ]

src/gevent/testing/testrunner.py

@@ -536,12 +536,16 @@ class Discovery(object):
             self.__add_test(qualified_name, filename, contents)
 
         def visit_files(self, filenames):
+            print("\tBegin visit")
             for filename in filenames:
+                print("\tVisiting", filename)
                 self.visit_file(filename)
             with Discovery._in_dir(self.orig_dir):
                 self.__expand_imports()
             self.__combine_commands(self.std_monkey_patch_files)
             self.__combine_commands(self.no_monkey_patch_files)
+            print("\tCommands", self.commands)
+            print("\tEnd visit")
 
     @staticmethod
     @contextmanager