Create initial 2.0 engine implementation

Implemented the SQLAlchemy 2 :func:`.future.create_engine` function which
is used for forwards compatibility with SQLAlchemy 2.   This engine
features always-transactional behavior with autobegin.

Allow execution options per statement execution.  This includes
that the before_execute() and after_execute() events now accept
an additional dictionary with these options, empty if not
passed; a legacy event decorator is added for backwards compatibility
which now also emits a deprecation warning.

Add some basic tests for execution, transactions, and
the new result object.   Build out on a new testing fixture
that swaps in the future engine completely to start with.

Change-Id: I70e7338bb3f0ce22d2f702537d94bb249bd9fb0a
Fixes: #4644

1 files changed, 8 insertions, 0 deletions

diff --git a/lib/sqlalchemy/testing/config.py b/lib/sqlalchemy/testing/config.py
index 140f5f782..e97821d72 100644
--- a/lib/sqlalchemy/testing/config.py
+++ b/lib/sqlalchemy/testing/config.py
@@ -150,6 +150,14 @@ class Config(object):
         cls.set_as_current(config, namespace)
 
     @classmethod
+    def pop(cls, namespace):
+        if cls._stack:
+            # a failed test w/ -x option can call reset() ahead of time
+            _current = cls._stack[-1]
+            del cls._stack[-1]
+            cls.set_as_current(_current, namespace)
+
+    @classmethod
     def reset(cls, namespace):
         if cls._stack:
             cls.set_as_current(cls._stack[0], namespace)