Fix database migrations

The pattern of adding a column and then reading a table with it
no longer works in SQLAlchemy 1.3.20. This has been reported
upstream [1].

[1] https://github.com/sqlalchemy/sqlalchemy/issues/5669

Change-Id: I5fd1deeef9cf70794bc61c101e1d7d4379d4b96b
(cherry picked from commit f5cf6b958c)

magnum/db/sqlalchemy/alembic/versions/1d045384b966_add_insecure_baymodel_attr.py

@@ -28,7 +28,8 @@ import sqlalchemy as sa  # noqa: E402
 def upgrade():
     insecure_column = sa.Column('insecure', sa.Boolean(), default=False)
     op.add_column('baymodel', insecure_column)
-    baymodel = sa.sql.table('baymodel', insecure_column)
+    baymodel = sa.sql.table('baymodel',
+                            sa.Column('insecure', sa.Boolean(), default=False))
     op.execute(
         baymodel.update().values({'insecure': True})
     )

releasenotes/notes/migrations-1.3.20-60e5f990422f2ca5.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    Fixes database migrations with SQLAlchemy 1.3.20.