Limit dnspython to < 2.3.0 until eventlet incompatibitliy is solved

[potiuk]

The dnspython has been released 2 hours ago and apparently eventlet that cassandra-driver uses is not compatible with the new version.

Until the problem is fixed, we should limit dnspython to <2.3.0.

Related: eventlet/eventlet#781

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[potiuk]

@ephraimbuddy @pierrejeambrun -> in case you will be pushing a new version of v2_5_test, likely that one should be cherry-picked. It is only relevant for the reason of constraints - because it turns out that new dnspython is not compatible with the way how cassandra driver + eventlet patch the dnspython during import (and fail) so it would be good when next constraints are regenerated for 2.5, the dnspython is not upgraded to 2.3.0.

[potiuk]

Looks like I also had to do the same with "async" extra of Airlow @pierrejeambrun to keep PROD images being built.

[ashb]

Not sure about the dnspython being added to async packages extra group though?

[potiuk]

Not sure about the dnspython being added to async packages extra group though?

I think, it is the easiest way to handle the problem. The problem is that whenever eventlet is installed and imported, it attempts to patch dnspython if it finds it during import (!) (and fails when dnspython 2.3.0 is installed).

So basically when we install eventlet we should never, ever (until it is fixed) allow dnspython >=2.3.0 to be installed, because importing eventlet will fail 🤷

The only way to do it is to add dnspython in all extras that also install eventlet (we have no other way to limit dnspython but adding it to extra's requires).

[potiuk]

BTW. Kudos to @mik-laj for adding the PROD image unit tests - because those tests (running imports of a number of extras we have there) detected that we also need to fix the async extra.

[potiuk]

All looks good. Merging.