bpo-38659: [Enum] add _simple_enum decorator (GH-25497)

add:

* `_simple_enum` decorator to transform a normal class into an enum
* `_test_simple_enum` function to compare
* `_old_convert_` to enable checking `_convert_` generated enums

`_simple_enum` takes a normal class and converts it into an enum:

    @simple_enum(Enum)
    class Color:
        RED = 1
        GREEN = 2
        BLUE = 3

`_old_convert_` works much like` _convert_` does, using the original logic:

    # in a test file
    import socket, enum
    CheckedAddressFamily = enum._old_convert_(
            enum.IntEnum, 'AddressFamily', 'socket',
            lambda C: C.isupper() and C.startswith('AF_'),
            source=_socket,
            )

`_test_simple_enum` takes a traditional enum and a simple enum and
compares the two:

    # in the REPL or the same module as Color
    class CheckedColor(Enum):
        RED = 1
        GREEN = 2
        BLUE = 3

    _test_simple_enum(CheckedColor, Color)

    _test_simple_enum(CheckedAddressFamily, socket.AddressFamily)

Any important differences will raise a TypeError

Lib/test/test_ssl.py

@@ -12,6 +12,8 @@ from test.support import warnings_helper
 import socket
 import select
 import time
+import datetime
+import enum
 import gc
 import os
 import errno
@@ -31,7 +33,7 @@ except ImportError:
 
 ssl = import_helper.import_module("ssl")
 
-from ssl import TLSVersion, _TLSContentType, _TLSMessageType
+from ssl import TLSVersion, _TLSContentType, _TLSMessageType, _TLSAlertType
 
 Py_DEBUG = hasattr(sys, 'gettotalrefcount')
 Py_DEBUG_WIN32 = Py_DEBUG and sys.platform == 'win32'
@@ -4697,6 +4699,155 @@ class TestSSLDebug(unittest.TestCase):
                 s.connect((HOST, server.port))
 
 
+class TestEnumerations(unittest.TestCase):
+
+    def test_tlsversion(self):
+        class CheckedTLSVersion(enum.IntEnum):
+            MINIMUM_SUPPORTED = _ssl.PROTO_MINIMUM_SUPPORTED
+            SSLv3 = _ssl.PROTO_SSLv3
+            TLSv1 = _ssl.PROTO_TLSv1
+            TLSv1_1 = _ssl.PROTO_TLSv1_1
+            TLSv1_2 = _ssl.PROTO_TLSv1_2
+            TLSv1_3 = _ssl.PROTO_TLSv1_3
+            MAXIMUM_SUPPORTED = _ssl.PROTO_MAXIMUM_SUPPORTED
+        enum._test_simple_enum(CheckedTLSVersion, TLSVersion)
+
+    def test_tlscontenttype(self):
+        class Checked_TLSContentType(enum.IntEnum):
+            """Content types (record layer)
+
+            See RFC 8446, section B.1
+            """
+            CHANGE_CIPHER_SPEC = 20
+            ALERT = 21
+            HANDSHAKE = 22
+            APPLICATION_DATA = 23
+            # pseudo content types
+            HEADER = 0x100
+            INNER_CONTENT_TYPE = 0x101
+        enum._test_simple_enum(Checked_TLSContentType, _TLSContentType)
+
+    def test_tlsalerttype(self):
+        class Checked_TLSAlertType(enum.IntEnum):
+            """Alert types for TLSContentType.ALERT messages
+
+            See RFC 8466, section B.2
+            """
+            CLOSE_NOTIFY = 0
+            UNEXPECTED_MESSAGE = 10
+            BAD_RECORD_MAC = 20
+            DECRYPTION_FAILED = 21
+            RECORD_OVERFLOW = 22
+            DECOMPRESSION_FAILURE = 30
+            HANDSHAKE_FAILURE = 40
+            NO_CERTIFICATE = 41
+            BAD_CERTIFICATE = 42
+            UNSUPPORTED_CERTIFICATE = 43
+            CERTIFICATE_REVOKED = 44
+            CERTIFICATE_EXPIRED = 45
+            CERTIFICATE_UNKNOWN = 46
+            ILLEGAL_PARAMETER = 47
+            UNKNOWN_CA = 48
+            ACCESS_DENIED = 49
+            DECODE_ERROR = 50
+            DECRYPT_ERROR = 51
+            EXPORT_RESTRICTION = 60
+            PROTOCOL_VERSION = 70
+            INSUFFICIENT_SECURITY = 71
+            INTERNAL_ERROR = 80
+            INAPPROPRIATE_FALLBACK = 86
+            USER_CANCELED = 90
+            NO_RENEGOTIATION = 100
+            MISSING_EXTENSION = 109
+            UNSUPPORTED_EXTENSION = 110
+            CERTIFICATE_UNOBTAINABLE = 111
+            UNRECOGNIZED_NAME = 112
+            BAD_CERTIFICATE_STATUS_RESPONSE = 113
+            BAD_CERTIFICATE_HASH_VALUE = 114
+            UNKNOWN_PSK_IDENTITY = 115
+            CERTIFICATE_REQUIRED = 116
+            NO_APPLICATION_PROTOCOL = 120
+        enum._test_simple_enum(Checked_TLSAlertType, _TLSAlertType)
+
+    def test_tlsmessagetype(self):
+        class Checked_TLSMessageType(enum.IntEnum):
+            """Message types (handshake protocol)
+
+            See RFC 8446, section B.3
+            """
+            HELLO_REQUEST = 0
+            CLIENT_HELLO = 1
+            SERVER_HELLO = 2
+            HELLO_VERIFY_REQUEST = 3
+            NEWSESSION_TICKET = 4
+            END_OF_EARLY_DATA = 5
+            HELLO_RETRY_REQUEST = 6
+            ENCRYPTED_EXTENSIONS = 8
+            CERTIFICATE = 11
+            SERVER_KEY_EXCHANGE = 12
+            CERTIFICATE_REQUEST = 13
+            SERVER_DONE = 14
+            CERTIFICATE_VERIFY = 15
+            CLIENT_KEY_EXCHANGE = 16
+            FINISHED = 20
+            CERTIFICATE_URL = 21
+            CERTIFICATE_STATUS = 22
+            SUPPLEMENTAL_DATA = 23
+            KEY_UPDATE = 24
+            NEXT_PROTO = 67
+            MESSAGE_HASH = 254
+            CHANGE_CIPHER_SPEC = 0x0101
+        enum._test_simple_enum(Checked_TLSMessageType, _TLSMessageType)
+
+    def test_sslmethod(self):
+        Checked_SSLMethod = enum._old_convert_(
+                enum.IntEnum, '_SSLMethod', 'ssl',
+                lambda name: name.startswith('PROTOCOL_') and name != 'PROTOCOL_SSLv23',
+                source=ssl._ssl,
+                )
+        enum._test_simple_enum(Checked_SSLMethod, ssl._SSLMethod)
+
+    def test_options(self):
+        CheckedOptions = enum._old_convert_(
+                enum.FlagEnum, 'Options', 'ssl',
+                lambda name: name.startswith('OP_'),
+                source=ssl._ssl,
+                )
+        enum._test_simple_enum(CheckedOptions, ssl.Options)
+
+
+    def test_alertdescription(self):
+        CheckedAlertDescription = enum._old_convert_(
+                enum.IntEnum, 'AlertDescription', 'ssl',
+                lambda name: name.startswith('ALERT_DESCRIPTION_'),
+                source=ssl._ssl,
+                )
+        enum._test_simple_enum(CheckedAlertDescription, ssl.AlertDescription)
+
+    def test_sslerrornumber(self):
+        Checked_SSLMethod = enum._old_convert_(
+                enum.IntEnum, '_SSLMethod', 'ssl',
+                lambda name: name.startswith('PROTOCOL_') and name != 'PROTOCOL_SSLv23',
+                source=ssl._ssl,
+                )
+        enum._test_simple_enum(Checked_SSLMethod, ssl._SSLMethod)
+
+    def test_verifyflags(self):
+        CheckedVerifyFlags = enum._old_convert_(
+                enum.FlagEnum, 'VerifyFlags', 'ssl',
+                lambda name: name.startswith('VERIFY_'),
+                source=ssl._ssl,
+                )
+        enum._test_simple_enum(CheckedVerifyFlags, ssl.VerifyFlags)
+
+    def test_verifymode(self):
+        CheckedVerifyMode = enum._old_convert_(
+                enum.IntEnum, 'VerifyMode', 'ssl',
+                lambda name: name.startswith('CERT_'),
+                source=ssl._ssl,
+                )
+        enum._test_simple_enum(CheckedVerifyMode, ssl.VerifyMode)
+
 def test_main(verbose=False):
     if support.verbose:
         plats = {