GitLab

* use f-string

* delete python3.5 sup

* minor fix

* fix supported python version

* fix format

* fix yapf

* remove redundant space

* fix typo

* remove supports for python 2.7

* fix the unit test for python 3.5

* add python 3.8 in CI

* try ubuntu 18.04 as the environment

Signed-off-by: lizz <lizz@sensetime.com>

* fix requirements

* don't reuse build dependencies between different envs

* minor fix

* change the order of opencv and opencv-headless