In the master branch, .gitattributes now contains:
---
*.pck binary
Lib/test/cjkencodings/* binary
Lib/test/decimaltestdata/*.decTest binary
Lib/test/sndhdrdata/sndhdr.* binary
Lib/test/test_email/data/msg_26.txt binary
Lib/test/xmltestdata/* binary
Lib/venv/scripts/nt/* binary
Lib/test/coding20731.py binary
---

History of the file:
---
$ git log --follow .gitattributes  
commit 060d2d776a29341c079cce37220324f9775140ba
Author: INADA Naoki <methane@users.noreply.github.com>
Date:   Sun Mar 5 08:49:45 2017 +0900

    remove merge=union attribute for Misc/NEWS (GH-460)
    
    Github doesn't support it (ref. isaacs/github#487).  So it can't ease
    conflict on Github.
    
    Additionally, it can make trouble when cherry-pick. (ref. GH-212)

commit 2771304357607aa62801a67acc1e3c7c8ec489ce
Author: Benjamin Peterson <benjamin@python.org>
Date:   Wed Feb 22 22:38:48 2017 -0800

    mark various test data binary (#233)

commit 2c700af5a761f83f303cc7295b660ac31f7d4ed1
Author: INADA Naoki <methane@users.noreply.github.com>
Date:   Tue Feb 21 18:39:41 2017 +0900

    .gitattribute -> .gitattributes (GH-213)

commit 3f3d0364a91aa8b89e175a49f93ad04dd4676186
Author: INADA Naoki <methane@users.noreply.github.com>
Date:   Tue Feb 21 18:17:06 2017 +0900

    Reduce conflict on Misc/NEWS (GH-212)
    
    use "union" merge strategy for Misc/NEWS.
---

test_random and test_sax now pass on my Windows VM... but still fail on the "AMD64 Windows8 3.x" buildbot :-(
http://buildbot.python.org/all/builders/AMD64%20Windows8%203.x/builds/461/steps/test/logs/stdio

Is it possible that Git on this buildbot ignores .gitattributes? Maybe the Git version is too old?