test_create_long_path fails ... when ... the ... path ... is ... long ...

[exarkun]

[ERROR]
Traceback (most recent call last):
  File "/nix/store/sp2j3hg0cq8pnvz7mwa0d9abns89vkib-python2.7-tahoe-lafs-1.11.1/lib/python2.7/site-packages/allmydata/test/test_util.py", line 524, in test_create_long_path
    fileutil.write(long_path, "test")
  File "/nix/store/sp2j3hg0cq8pnvz7mwa0d9abns89vkib-python2.7-tahoe-lafs-1.11.1/lib/python2.7/site-packages/allmydata/util/fileutil.py", line 230, in write
    wf = open(path, mode)
exceptions.IOError: [Errno 36] File name too long: u'/tmp/nix-build-python2.7-tahoe-lafs-1.11.1.drv-0/tahoe-lafs-1.11.0/_trial_temp/test_create_long_path/xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx'

allmydata.test.test_util.FileUtil.test_create_long_path

I don't understand the point of this test at all.