Gracefully degrade on v$transaction not readable

Fixed regression which occured due to [ticket:5755] which implemented
isolation level support for Oracle.   It has been reported that many Oracle
accounts don't actually have permission to query the ``v$transaction``
view so this feature has been altered to gracefully fallback when it fails
upon database connect, where the dialect will assume "READ COMMITTED" is
the default isolation level as was the case prior to SQLAlchemy 1.3.21.
However, explicit use of the :meth:`_engine.Connection.get_isolation_level`
method must now necessarily raise an exception, as Oracle databases with
this restriction explicitly disallow the user from reading the current
isolation level.

Fixes: #5784
Change-Id: Iefc82928744f3c944c18ae8000eb3c9e52e523bc

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/sqlalchemy/testing/suite/test_dialect.py b/lib/sqlalchemy/testing/suite/test_dialect.py
index 6a5f2d91b..8709aca9d 100644
--- a/lib/sqlalchemy/testing/suite/test_dialect.py
+++ b/lib/sqlalchemy/testing/suite/test_dialect.py
@@ -1,6 +1,5 @@
 #! coding: utf-8
 
-from sqlalchemy import event
 from .. import assert_raises
 from .. import config
 from .. import engines
@@ -12,6 +11,7 @@ from ..config import requirements
 from ..provision import set_default_schema_on_connection
 from ..schema import Column
 from ..schema import Table
+from ... import event
 from ... import exc
 from ... import Integer
 from ... import literal_column