bpo-37322: ssl test_pha_required_nocert() ignores expected SSLError (GH-14670)

test_ssl.test_pha_required_nocert() now uses
support.catch_threading_exception() to ignore the expected SSLError
in ConnectionHandler of ThreadedEchoServer (it is only raised
sometimes on Windows).

Lib/test/test_ssl.py

@@ -4326,21 +4326,24 @@ class TestPostHandshakeAuth(unittest.TestCase):
         server_context.verify_mode = ssl.CERT_REQUIRED
         client_context.post_handshake_auth = True
 
-        server = ThreadedEchoServer(context=server_context, chatty=False)
-        with server:
-            with client_context.wrap_socket(socket.socket(),
-                                            server_hostname=hostname) as s:
-                s.connect((HOST, server.port))
-                s.write(b'PHA')
-                # receive CertificateRequest
-                self.assertEqual(s.recv(1024), b'OK\n')
-                # send empty Certificate + Finish
-                s.write(b'HASCERT')
-                # receive alert
-                with self.assertRaisesRegex(
-                        ssl.SSLError,
-                        'tlsv13 alert certificate required'):
-                    s.recv(1024)
+        # Ignore expected SSLError in ConnectionHandler of ThreadedEchoServer
+        # (it is only raised sometimes on Windows)
+        with support.catch_threading_exception() as cm:
+            server = ThreadedEchoServer(context=server_context, chatty=False)
+            with server:
+                with client_context.wrap_socket(socket.socket(),
+                                                server_hostname=hostname) as s:
+                    s.connect((HOST, server.port))
+                    s.write(b'PHA')
+                    # receive CertificateRequest
+                    self.assertEqual(s.recv(1024), b'OK\n')
+                    # send empty Certificate + Finish
+                    s.write(b'HASCERT')
+                    # receive alert
+                    with self.assertRaisesRegex(
+                            ssl.SSLError,
+                            'tlsv13 alert certificate required'):
+                        s.recv(1024)
 
     def test_pha_optional(self):
         if support.verbose: