Opens database connection.

def _open_sqlite(db_file):
    """Opens database connection."""
    db_file = os.path.expanduser(db_file)
    try:
        with open(db_file):
            # test that the file can be accessed
            pass
        return sqlite3.connect(db_file, detect_types=sqlite3.PARSE_DECLTYPES)
    except (IOError, sqlite3.Error) as err:
        raise Dump2PolarionException("{}".format(err))