Change import of pysqlite2.dbapi2 to sqlite3 in file_test_path.py

In 8bf90117af6927041b646ba5e84fa4b59cb87bf1 and #48 all imports of `pysqlite2.dbapi2` were replaced by `sqlite3 `.

The file file_test_path.py was forgotten.
Here we changed the import as well.