Update Dockerfile for py3.9 (#1223)

* Update pre-commit conifg

Update gitlint to 0.15.1
Update flake8 til 3.9.2
Update isort to 5.9.3
Update pre-commit-hooks to 4.0.1

* Add support for python 3.9

python 3.9 has finally removed Thread.isAlive() function.
but because we still (?) need to support python version w/o is_alive() we need to check for both

* Update requirements

Python3.9 does not have sources for some of the old library versions MAD expects
Gevent updated to version 20.9
Greenlet updated to version 1.1
OpenCV updated to version 4.4

* Update toxt and docker-dev

Add python 3.9 to test suite
Remove exclude for questgen.py
add N818 to tox ignore (requires a lot of fixing in apk:wizard: to solve)

* Lint questgen

* Tell flake8 about _

* WIP Update mysqlclient requirement to 2.0.3

* Upgrade requirements to be more in sync with redis-mitm-branch

* Update Dockerfile

Co-authored-by: fosJoddie <[email protected]>

Author: jinnatar

Dockerfile

@@ -1,7 +1,7 @@
 ############################
 # MAD
 ############################
-FROM python:3.7-slim AS mad-core
+FROM python:3.9-slim AS mad-core
 # Working directory for the application
 WORKDIR /usr/src/app
 

requirements.txt

@@ -28,4 +28,4 @@ psutil~=5.6
 pytesseract~=0.3
 requests~=2.22
 s2sphere~=0.2
-websockets>=7
+websockets>=7