fix pypy build
fix pypy build

PyPy (>= 3.6) was consistently erroring out during `pokedex load`,
with the error

    OperationalError: (_sqlite3.OperationalError) cannot commit transaction - SQL statements in progress (Background on this error at: http://sqlalche.me/e/e3q8)

It turns out PyPy was not garbage collecting something, causing a
database cursor to be left open. See the giant comment block for
details.

veekun/pokedex,veekun/pokedex