Debian Buster only ships with a JDK11, and Hive/Hadoop fails in odd,
hard to debug ways (complains about metastore not being initalized,
possibly related to the class loader issues.)

Until we rip Hive out from the CI (replacing it with Hadoop in a seprate
integration, only on for some builds) we'll have to stick with JRE8

Our previous approach of installing openjdk-8 from Sid/Unstable started
failing as Debian Sid has a new (and conflicting) version of GCC/libc.
The adoptopenjdk package archive is designed for Buster so should be
more resilient

…pache#8910)

Currently there is no way to determine the state of a TaskInstance in the graph view or tree view for people with colour blindness

Approximately 4.5% of people experience some form of colour vision deficiency

The singularity operator tests _have always_ used mocking, so we were
adding 700MB to our docker image for nothing.

Fixes apache#8774

…e#8944)

CSRF_ENABLED does nothing.

Thankfully, due to sensible defaults in flask-wtf, CSRF is on by
default, but we should set this correctly.

Fixes apache#8915

…#8949)

All PRs will used cached "latest good" version of the python
base images from our GitHub registry. The python versions in
the Github Registry will only get updated after a master
build (which pulls latest Python image from DockerHub) builds
and passes test correctly.

This is to avoid problems that we had recently with Python
patchlevel releases breaking our Docker builds.

)

Slight "improvement" on apache#8949

…c dag (apache#8952)

The scheduler_dag_execution_timing script wants to run _n_ dag runs to
completion. However since the start date of those dags is Dynamic (`now
- delta`) we can't pre-compute the execution_dates like we were before.
(This is because the execution_date of the very first dag run would be
`now()` of the parser process, but if we try to pre-compute that in
the benchmark process it would see a different value of now().)

This PR changes it to instead watch for the first _n_ dag runs to be
completed. This should make it work with more dags with less changes to
them.

* Push CI images to Docker packcage cache for v1-10 branches

This is done as a commit to master so that we can keep the two branches
in sync

Co-Authored-By: Ash Berlin-Taylor <ash_github@firemirror.com>

* Run Github Actions against v1-10-stable too

Co-authored-by: Ash Berlin-Taylor <ash_github@firemirror.com>

Old Repo: https://github.com/Azure/azure-cosmos-python
New Repo: https://github.com/Azure/azure-sdk-for-python/tree/master/sdk/cosmos/azure-cosmos

azure-cosmos==4.0.0 was released on 20 May 2020 that breaks Airflow

`field_path` was renamed to `tag_template_field_path` in >=0.8 and there might be other unknown errors

add return XComArg

…__call__

handle empty dict/list in sequencial calls

revert unnecessary dependency addition

s/Exception/AirflowException

make pythonfunctionaloperator a private class

missing documentation

remove docs

remove linter errors

migrate to pytest

use DagRunType and fix small issue w XComArg

some more pylint fixes

pylint and isort issues

add task into STATICA_HACK

remove cyclic dependency

disable pylint nomember for .key

remove unneded line

address mypy issues

fix more pylint mypy issues

fix docs

add _called variable

change task decorator name to operator