Instead of checking get_tables, just check the COLUMN_INDEX.

This reduces the number of frivolous sql queries we make, since
the index contians all the tables anyway. The side effect is that
the function won't acknowledge tables created during the run time,
which I kind of think is a good thing since it reduces accident
surface area to the tables outlined by the programmer during init.

voussoirkit/worms.py

@@ -122,7 +122,7 @@ class Database(metaclass=abc.ABCMeta):
         raise NotImplementedError
 
     def assert_table_exists(self, table) -> None:
-        if table not in self.get_tables():
+        if table not in self.COLUMN_INDEX:
             raise BadTable(f'Table {table} does not exist.')
 
     def close(self):