fully support isolation_level parameter in base dialect

Generalized the :paramref:`_sa.create_engine.isolation_level` parameter to
the base dialect so that it is no longer dependent on individual dialects
to be present. This parameter sets up the "isolation level" setting to
occur for all new database connections as soon as they are created by the
connection pool, where the value then stays set without being reset on
every checkin.

The :paramref:`_sa.create_engine.isolation_level` parameter is essentially
equivalent in functionality to using the
:paramref:`_engine.Engine.execution_options.isolation_level` parameter via
:meth:`_engine.Engine.execution_options` for an engine-wide setting. The
difference is in that the former setting assigns the isolation level just
once when a connection is created, the latter sets and resets the given
level on each connection checkout.

Fixes: #6342
Change-Id: Id81d6b1c1a94371d901ada728a610696e09e9741

1 files changed, 0 insertions, 16 deletions

diff --git a/test/dialect/test_sqlite.py b/test/dialect/test_sqlite.py
index f1efaf7a6..ca203ad8c 100644
--- a/test/dialect/test_sqlite.py
+++ b/test/dialect/test_sqlite.py
@@ -54,7 +54,6 @@ from sqlalchemy.testing import expect_warnings
 from sqlalchemy.testing import fixtures
 from sqlalchemy.testing import is_
 from sqlalchemy.testing import mock
-from sqlalchemy.testing.assertions import expect_raises_message
 from sqlalchemy.types import Boolean
 from sqlalchemy.types import Date
 from sqlalchemy.types import DateTime
@@ -597,21 +596,6 @@ class DialectTest(
                 )
             )
 
-    @testing.only_on("sqlite+pysqlite")
-    def test_isolation_level_message(self):
-        # needs to test that all three words are present and we also
-        # dont want to default all isolation level messages to use
-        # sorted(), so rely on python 3.7 for ordering of keywords
-        # in the message
-        with expect_raises_message(
-            exc.ArgumentError,
-            "Invalid value 'invalid' for "
-            "isolation_level. Valid isolation levels for "
-            "sqlite are READ UNCOMMITTED, SERIALIZABLE, AUTOCOMMIT",
-        ):
-            with testing.db.connect() as conn:
-                conn.execution_options(isolation_level="invalid")
-
     @testing.only_on("sqlite+pysqlcipher")
     def test_pysqlcipher_connects(self):
         """test #6586"""