[AIRFLOW-6766] Fix "cannot import ensure_text" error for pre-commit (#7393)
[AIRFLOW-6766] Fix "cannot import ensure_text" error for pre-commit (#7393)

* [AIRFLOW-6766] Fix "cannot import ensure_text" error for pre-commit

As of today Travis bundles six version 1.11.0 with their python
3.6 image and it misses ensure_text method. Bumping to 1.14+
solves the problem.

(cherry picked from commit 319714f07c470bca999b2f6becbb340c81e79e29)

owlabs/incubator-airflow,owlabs/incubator-airflow,owlabs/incubator-airflow,owlabs/incubator-airflow