Handle the case where the query return more than two values
    
    This should fix the error we're seeing in production:
    ````
      File "/code/mdapi-get_repo_md", line 232, in build_cache
        for pkgId, pkgname in conn.execute(query):
    ValueError: too many values to unpack (expected 2)
    ````
    
    Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>