[Sqlalchemy-tickets] Issue #3955: connectionless execution + autocommit + ON CONFLICT DO NOTHING + no rows == boom (zzzeek/sqlalchemy)

[Michael B. <iss...@bi...>]

New issue 3955: connectionless execution + autocommit + ON CONFLICT DO NOTHING + no rows == boom
https://bitbucket.org/zzzeek/sqlalchemy/issues/3955/connectionless-execution-autocommit-on

Michael Bayer:

```
#!diff

@@ -96,6 +97,33 @@ class OnConflictTest(fixtures.TablesTest):
                 [(1, 'name1')]
             )
 
+    def test_on_conflict_do_nothing_connectionless(self):
+        users = self.tables.users_xtra
+
+        with testing.db.connect() as conn:
+            result = conn.execute(
+                insert(users).on_conflict_do_nothing(
+                    constraint='uq_login_email'),
+
+                dict(name='name1', login_email='email1')
+            )
+            eq_(result.inserted_primary_key, [1])
+            eq_(result.returned_defaults, (1,))
+
+        result = testing.db.execute(
+            insert(users).on_conflict_do_nothing(
+                constraint='uq_login_email'
+            ),
+            dict(name='name2', login_email='email1')
+        )
+        eq_(result.inserted_primary_key, None)
+        eq_(result.returned_defaults, None)
+
+        eq_(
+            testing.db.execute(users.select().where(users.c.id == 1)).fetchall(),
+            [(1, 'name1', 'email1', None)]
+        )
+
     @testing.provide_metadata
     def test_on_conflict_do_nothing_target(self):
         users = self.tables.users

```

the lack of row returned sends the connection into autoclose via result.fetchone().  then autocommit causes an exception, then it continues to be confused because the connection has been closed.