build error on amd64 (cosmic ruby2.5 2.5.1-5ubuntu1)

[Christian Ehrhardt ]

Build time tests fail on recent upload:

  1) Failure:
TestIO#test_copy_stream_no_busy_wait [/<<PKGBUILDDIR>>/test/ruby/test_io.rb:549]:
r58534 [ruby-core:80969] [Backport #13533].
Expected 0.015999999999998238 to be <= 0.011000000000000001.

  2) Failure:
TestThread#test_thread_interrupt_for_killed_thread [/<<PKGBUILDDIR>>/test/ruby/test_thread.rb:1256]:
[Bug #8996]
pid 4234 killed by SIGABRT (signal 6) (core dumped)

Finished tests in 1004.988064s, 17.2400 tests/s, 2250.9123 assertions/s.
17326 tests, 2262140 assertions, 2 failures, 0 errors, 58 skips

ruby -v: ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-linux-gnu]
make[2]: *** [uncommon.mk:698: yes-test-almost] Error 2

From build log [1][2]

[1]: https://launchpadlibrarian.net/389975333/buildlog_ubuntu-cosmic-amd64.ruby2.5_2.5.1-5ubuntu1_BUILDING.txt.gz
[2]: https://launchpad.net/ubuntu/+source/ruby2.5/2.5.1-5ubuntu1/+build/15480188

[Christian Ehrhardt  (paelzer)]

Subscribing xnox who did the last upload.

@xnox
 - is this something you are aware of or have expected?
 - Do you think a build retry makes sense?

[Christian Ehrhardt  (paelzer)]

I didn't want to retrigger your upload since I don't own it.

But I spun up three PPAs to check if this build time test is flaky.
The following three just started building:
- https://launchpad.net/~ci-train-ppa-service/+archive/ubuntu/3431/+packages
- https://launchpad.net/~ci-train-ppa-service/+archive/ubuntu/3432/+packages
- https://launchpad.net/~ci-train-ppa-service/+archive/ubuntu/3433/+packages

[Christian Ehrhardt  (paelzer)]

- 1 build
  - no errors at all
- 1 build
  - amd64 error (1) of above
  - i386 error (1) of above
- 1 build
  - i386 error (1) of above

So it is a flaky test at build time.

@xnox - what do you want to do for now, just hit rebuild on x86 or try to resolve the issue right away.
At least in all my tries I only hit TestIO#test_copy_stream_no_busy_wait, so we might mask this test in paticular maybe?