[ci] Remove Python 2.7 CI jobs

[jameslamb]

Now that v3.1.0 has been released (#3484) and marked as the final release that supports Python 2.7 (#3565), I'd like to propose removing the Python 2.7 CI jobs.

This would unblock the work to move dask-lightgbm into this project (#3515 (comment)) and could help us save some credits on Travis while we deal with the issues caused by Travis's new announcements around ending support for open source projects (#3519).

I know there are other code-level things we could do to simplify lightgbm now that Python 2.7 support is being dropped, but I think cutting out the CI jobs is valuable enough that it's worth doing as a simple, standalone pull request.

[StrikerRUS]

You can't just remove sdist job. This job is very important as it emulates installation from PyPI source.

Instead, simply remove PYTHON_VERSION=2.7 part.

[StrikerRUS]

Also, I'd like to wait some time before actually dropping Python 2.7, because we might need to produce hotfix 3.1.1 version with Python 2.7 support.

[jameslamb]

You can't just remove sdist job. This job is very important as it emulates installation from PyPI source.

Instead, simply remove PYTHON_VERSION=2.7 part.

oh ok, does this mean that right now on master we don't have another job that emulates "installation from PyPi source" for Python 3.x?

[jameslamb]

Also, I'd like to wait some time before actually dropping Python 2.7, because we might need to produce hotfix 3.1.1 version with Python 2.7 support.

alright I can just close this for now, I guess.

[StrikerRUS]

oh ok, does this mean that right now on master we don't have another job that emulates "installation from PyPi source" for Python 3.x?

We have one for macOS

LightGBM/.vsts-ci.yml

Lines 81 to 82 in 0b5e60d

	sdist:
	TASK: sdist

[github-actions]

This pull request has been automatically locked since there has not been any recent activity since it was closed. To start a new related discussion, open a new issue at https://github.com/microsoft/LightGBM/issues including a reference to this.