exceptions: provide .message attribute for Py3K compatibility4.4.0

In two recent commits we fixed the way .message class attribute was
used by passing it as an argument to __init__() of the base Exception
class instead.

Unfortunately, this currently breaks Heat unit tests on Py3K as
exception instances no longer provide .message attribute there.

Re-introduce .message properties only for exception classes that used
to have them to ensure the new oslo.db release do not change the
interface of exceptions.

Closes-Bug: #1542961

Change-Id: I5cae408555956d77e6cbb4e5e513c1c6c375d29d

2 files changed, 21 insertions, 0 deletions

diff --git a/oslo_db/exception.py b/oslo_db/exception.py
index 715bbc1..c5e0fa9 100644
--- a/oslo_db/exception.py
+++ b/oslo_db/exception.py
@@ -43,6 +43,7 @@ with `try/except` statement. This is required for consistent handling of
 database errors.
 """
 
+import debtcollector.removals
 import six
 
 from oslo_db._i18n import _
@@ -147,6 +148,13 @@ class DBInvalidUnicodeParameter(Exception):
     without encoding directive.
     """
 
+    @debtcollector.removals.removed_property
+    def message(self):
+        # NOTE(rpodolyaka): provided for compatibility with python 3k, where
+        # exceptions do not have .message attribute, while we used to have one
+        # in this particular exception class. See LP #1542961 for details.
+        return str(self)
+
     def __init__(self):
         super(DBInvalidUnicodeParameter, self).__init__(
             _("Invalid Parameter: Encoding directive wasn't provided."))
@@ -184,6 +192,13 @@ class DBDataError(DBError):
 class InvalidSortKey(Exception):
     """A sort key destined for database query usage is invalid."""
 
+    @debtcollector.removals.removed_property
+    def message(self):
+        # NOTE(rpodolyaka): provided for compatibility with python 3k, where
+        # exceptions do not have .message attribute, while we used to have one
+        # in this particular exception class. See LP #1542961 for details.
+        return str(self)
+
     def __init__(self, key=None):
         super(InvalidSortKey, self).__init__(
             _("Sort key supplied is invalid: %s") % key)
diff --git a/oslo_db/tests/sqlalchemy/test_utils.py b/oslo_db/tests/sqlalchemy/test_utils.py
index 405619f..a3e7e1a 100644
--- a/oslo_db/tests/sqlalchemy/test_utils.py
+++ b/oslo_db/tests/sqlalchemy/test_utils.py
@@ -153,11 +153,17 @@ class TestPaginateQuery(test_base.BaseTestCase):
                          str(exception.InvalidSortKey()))
         self.assertEqual("Sort key supplied is invalid: lol",
                          str(exception.InvalidSortKey("lol")))
+        self.assertEqual("Sort key supplied is invalid: lol",
+                         exception.InvalidSortKey("lol").message)
 
     def test_invalid_unicode_paramater_str(self):
         self.assertEqual(
             "Invalid Parameter: Encoding directive wasn't provided.",
             str(exception.DBInvalidUnicodeParameter()))
+        self.assertEqual(
+            "Invalid Parameter: Encoding directive wasn't provided.",
+            exception.DBInvalidUnicodeParameter().message
+        )
 
     def test_paginate_query_attribute_error(self):
         sqlalchemy.asc(self.model.user_id).AndReturn('asc')