recent 2.13.x broke SerializationStabilityTest in scala-parallel-collections

[SethTisue]

this came up over at scala/community-build#1564 which changes the Scala 2.13 SHA from scala/scala@3ed3e3f to scala/scala@e623b15

https://scala-ci.typesafe.com/job/scala-2.13.x-jdk11-integrate-community-build/3693/artifact/logs/scala-parallel-collections-build.log shows

[scala-parallel-collections] [info] Test scala.SerializationStabilityTest.testAll started
[scala-parallel-collections] [error] Test scala.SerializationStabilityTest.testAll failed: java.io.InvalidClassException: scala.collection.immutable.OldHashMap; local class incompatible: stream classdesc serialVersionUID = -2425602972438308285, local class serialVersionUID = -6733093582541111701, took 0.125 sec
[scala-parallel-collections] [error]     at java.io.ObjectStreamClass.initNonProxy(ObjectStreamClass.java:689)

[SethTisue]

ohhhh... presumably this an expected consequence of scala/scala#9976 and I just need to update the test

fyi @lrytz

[lrytz]

Mhm.. It means there are some serializable classes that don't define an explicit @SerialVersionUID. The correct fix would be to find those classes, see their computed SVUIDs (when using 2.13.8), and add an annotation with that specific value. This is what I did in the PR (first commit, scala/scala@003dc97).

[SethTisue]

oh okay, I'll do that.

[SethTisue]

PR scala/scala-parallel-collections#220

[SethTisue]

[info] Report from the dbuild run for dbuild: 
...
[info] Project scala-parallel-collections--: SUCCESS (project rebuilt ok)