Since build 305 (commit a40675c659cd8c0699f85ee9ac31660f93f8c2f5), test_importlib fails on AMD64 Windows8.1 Non-Debug 3.x:
https://buildbot.python.org/all/#/builders/405/builds/305

The last successful build wa the build 304 (commit ee03bad25e83b00ba5fc2a0265b48c6286e6b3f7).

Sadly, the test doesn't report the 'actual' variable value when the test fails.

======================================================================
FAIL: test_read_bytes (test.test_importlib.test_files.OpenNamespaceTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "D:\buildarea\3.x.ware-win81-release.nondebug\build\lib\test\test_importlib\test_files.py", line 14, in test_read_bytes
    assert actual == b'Hello, UTF-8 world!\n'
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError

Interesting commits from:
$ git log  ee03bad25e83b00ba5fc2a0265b48c6286e6b3f7..a40675c659cd8c0699f85ee9ac31660f93f8c2f5  

commit aaa83cdfab6817446285e631232f64b394ac6791
Author: Jason R. Coombs <jaraco@jaraco.com>
Date:   Thu Jul 29 21:05:05 2021 -0400

    bpo-44771: Apply changes from importlib_resources 5.2.1 (GH-27436)
    
    * bpo-44771: Apply changes from 3b24bd6307">importlib_resources@3b24bd6307
    
    * Add blurb
    
    * Exclude namespacedata01 from eol conversion.

Maybe Git does change the end of line of Lib/test/test_importlib/namespacedata01/utf-8.file file, even if .gitattributes contains:
"Lib/test/test_importlib/namespacedata01/* -text"

There is an issue where that file originally got EOL conversions, so all Windows buildbots were failing (issue44779).

I'd thought we'd worked around the issue by pushing out a PR that deleted the file and ensuring it ran on the buildbots (https://github.com/python/cpython/pull/27436#issuecomment-890029487).

I knew it was a risk, however, that either that PR failed to checkout on the buildbot, checked out on a different shard, or that another PR subsequently managed to check out the code without the .gitattributes fix.

I'm going to attempt that technique again and see if it's sufficient to bypass the symptom.

I've submitted a PR that deletes the file and requested it be built by the buildbots, but I also see that that bot hasn't built anything in 7 days (https://buildbot.python.org/all/#/builders/405), so I'm not hopeful my request for it to build that change will have any effect on that builder.

I'm not confident that I can get the message to the buildbot, so I sent a message to python-buildbots@python.org requesting to run the workaround on the buildbot. The message was flagged for moderation. My hope is that eventually goes through and will address the issue.

The builder is now passing after the buildbot owner reset the checkout.