[FLINK-20997][tests] Generate yarn classpath before test phase

[link3280]

What is the purpose of the change

YarnTestBase depends on classpaths generated by Maven dependency plugin in package phase, but YarnTestBaseTest is a unit test that executed in test phase (which is before package), so it's unable to find yarn.classpath and causes NPE.

Brief change log

Make the classpath generated in process-test-resources phase.

Verifying this change

This change is already covered by existing tests.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn/Mesos, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? (not applicable / docs / JavaDocs / not documented)

[flinkbot]

Thanks a lot for your contribution to the Apache Flink project. I'm the @flinkbot. I help the community
to review your pull request. We will use this comment to track the progress of the review.

Automated Checks

Last check on commit da7f00f (Fri May 28 07:09:55 UTC 2021)

Warnings:

• 1 pom.xml files were touched: Check for build and licensing issues.
• No documentation files were touched! Remember to keep the Flink docs up to date!

_{Mention the bot in a comment to re-run the automated checks.}

Review Progress

• ❓ 1. The [description] looks good.
• ❓ 2. There is [consensus] that the contribution should go into to Flink.
• ❓ 3. Needs [attention] from.
• ❓ 4. The change fits into the overall [architecture].
• ❓ 5. Overall code [quality] is good.

Please see the Pull Request Review Guide for a full explanation of the review process.

The Bot is tracking the review progress through labels. Labels are applied according to the order of the review items. For consensus, approval by a Flink committer of PMC member is required

Bot commands

The @flinkbot bot supports the following commands:

• @flinkbot approve description to approve one or more aspects (aspects: description, consensus, architecture and quality)
• @flinkbot approve all to approve all aspects
• @flinkbot approve-until architecture to approve everything until architecture
• @flinkbot attention @username1 [@username2 ..] to require somebody's attention
• @flinkbot disapprove architecture to remove an approval you gave earlier

[flinkbot]

CI report:

• da7f00f Azure: SUCCESS

Bot commands

The @flinkbot bot supports the following commands:

• @flinkbot run travis re-run the last Travis build
• @flinkbot run azure re-run the last Azure build

[XComp]

Thanks for looking into that @link3280. The issues description makes sense to me. I verified the change running mvn -pl flink-yarn-tests -Dtest=YARNSessionCapacitySchedulerITCase clean test

@rmetzger What I don't understand is why this didn't show up in the master builds assuming that the builds run from scratch in a newly created folder? 🤔

[rmetzger]

The build on Azure is quite customized (compile and test execution are executed separately) .. that's why this oversight didn't surface earlier.

Thanks a lot for this fix! Merging!