BUG31060730: Skip pure Python tests if Protobuf is not available

Some X DevAPI tests fail if Python Protobuf is not installed.
This patch skip tests that require the pure Python implementation
of Protobuf.

Author: nmariz

lib/mysqlx/protobuf/__init__.py

@@ -1,4 +1,4 @@
-# Copyright (c) 2017, 2019, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2017, 2020, Oracle and/or its affiliates. All rights reserved.
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License, version 2.0, as
@@ -196,7 +196,7 @@
         [(_MESSAGES[key], val) for key, val in _SERVER_MESSAGES_TUPLES]
     )
     HAVE_PROTOBUF = True
-
+    HAVE_PROTOBUF_ERROR = None
 
     class _mysqlxpb_pure(object):
         """This class implements the methods in pure Python used by the
@@ -236,10 +236,11 @@ def parse_server_message(msg_type, payload):
             msg = _mysqlxpb_pure.new_message(msg_type_name)
             msg.ParseFromString(payload)
             return msg
-except ImportError:
+except ImportError as err:
     HAVE_PROTOBUF = False
+    HAVE_PROTOBUF_ERROR = err
     if not HAVE_MYSQLXPB_CEXT:
-        raise ImportError("Protobuf is not available")
+        raise ImportError("Protobuf is not available: {}".format(err))
 
 CRUD_PREPARE_MAPPING = {
     "Mysqlx.ClientMessages.Type.CRUD_FIND": (
@@ -271,7 +272,8 @@ def set_use_pure(use_pure):
             use_pure (bool): `True` to use pure Python implementation.
         """
         if use_pure and not HAVE_PROTOBUF:
-            raise ImportError("Protobuf is not available")
+            raise ImportError("Protobuf is not available: {}"
+                              "".format(HAVE_PROTOBUF_ERROR))
         elif not use_pure and not HAVE_MYSQLXPB_CEXT:
             raise ImportError("MySQL X Protobuf C extension is not available")
         Protobuf.mysqlxpb = _mysqlxpb_pure if use_pure else _mysqlxpb

tests/test_mysqlx_connection.py

@@ -53,7 +53,8 @@
 from mysqlx.errors import InterfaceError, OperationalError, ProgrammingError
 from mysqlx.protocol import (Message, MessageReader, MessageWriter, Protocol,
                              HAVE_LZ4)
-from mysqlx.protobuf import HAVE_MYSQLXPB_CEXT, mysqlxpb_enum, Protobuf
+from mysqlx.protobuf import (HAVE_MYSQLXPB_CEXT, HAVE_PROTOBUF, mysqlxpb_enum,
+                             Protobuf)
 from mysql.connector.utils import linux_distribution
 from mysql.connector.version import VERSION, LICENSE
 
@@ -1330,6 +1331,7 @@ def test_disabled_x_protocol(self):
         self.assertRaises(ProgrammingError, mysqlx.get_session, settings)
 
     @unittest.skipIf(HAVE_MYSQLXPB_CEXT == False, "C Extension not available")
+    @unittest.skipUnless(HAVE_PROTOBUF, "Protobuf not available")
     def test_use_pure(self):
         settings = self.connect_kwargs.copy()
         settings["use-pure"] = False
@@ -1752,6 +1754,7 @@ def test_initial_empty_notice_cext(self):
         self.assertEqual(rows[0][0], "information_schema")
         session.close()
 
+    @unittest.skipUnless(HAVE_PROTOBUF, "Protobuf not available")
     def test_initial_empty_notice_pure(self):
         connect_kwargs = self.connect_kwargs.copy()
         host = "localhost"
@@ -1785,6 +1788,7 @@ def test_initial_notice_cext(self):
         self.assertEqual(rows[0][0], "information_schema")
         session.close()
 
+    @unittest.skipUnless(HAVE_PROTOBUF, "Protobuf not available")
     def test_initial_notice_pure(self):
         connect_kwargs = self.connect_kwargs.copy()
         host = "localhost"