Sqlite3.OperationalError: too many attached databases - max 10

import sqlite3


def create_table(db_name, values):
    con = sqlite3.connect("./databases/%s.db" % db_name)
    cur = con.cursor()
    cur.execute(
        '''CREATE TABLE fournisseurs(
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            nom TEXT
        )'''
    )
    s = ','.join(('(?)',) * len(values))
    cur.execute('INSERT INTO fournisseurs(nom) VALUES %s' % s, values)
    con.commit()
    con.close()


def tables_dif(main_db_name, *db_names):
    con = sqlite3.connect(":memory:")
    con.execute("ATTACH DATABASE './databases/%s.db' AS main_db" % main_db_name)
    cur = con.cursor()
    res = {}
    for db_name in db_names:
        con.execute("ATTACH DATABASE './databases/%s.db' AS db" % db_name)
        sql = '''
        SELECT t2.id, t2.nom
        FROM db.fournisseurs as t2
        LEFT JOIN main_db.fournisseurs as t
        USING(nom)
        WHERE t.nom IS NULL
        '''
        cur.execute(sql)
        res[db_name] = cur.fetchall()
        con.execute("DETACH DATABASE db")
    con.close()
    return res


try:
    create_table('main', ('jojo', 'mimi', 'riri'))
    create_table('base1', ('jojo', 'riri', 'vévé'))
    create_table('base2', ('riri', 'lulu'))
except:
    pass

print(tables_dif('main', 'base1', 'base2'))