Delete the public DB schema directly

Extracted from #188
as a separate PR.

pyramid-app/{{ cookiecutter.slug }}/{{ cookiecutter.package_name }}/scripts/init_db.py

@@ -48,7 +48,16 @@ def delete(engine: Engine) -> None:
     else:
         pre_delete(engine)
 
-    Base.metadata.drop_all(engine)
+    with engine.connect() as connection:
+        # Delete the DB's "public" schema directly.
+        # We do this instead of using SQLAlchemy's drop_all() because we want
+        # to delete *all* tables in the DB, not just the ones that SQLAlchemy
+        # knows about from the current codebase.
+        # For example this will delete tables created by migrations in other
+        # branches.
+        connection.execute(text("DROP SCHEMA PUBLIC CASCADE;"))
+        connection.execute(text("CREATE SCHEMA PUBLIC;"))
+        connection.execute(text("COMMIT;"))
 
     try:
         from {{ cookiecutter.package_name }}.db import post_delete