`sdist` fails with permission denied error after writing to a temp dir

Version info:
python 3.6.7, pip version 19.0.2, setuptools version v40.8.0, virtualenv v15.1.0, (ubuntu bionic)

When I use python setup.py install, an archive file dist/repro-0.0.0-py3.6.egg is created which contains repro/GITVER.txt. However (and perhaps this has to do with my misunderstanding of the semantics of data_files), when I run python setup.py sdist, I get error: could not create '../../../tmp': Permission denied.

The following minimal setup.py reproduces the problem:

from setuptools import setup
import os, tempfile

commithash = '000000'
tmpdir = tempfile.mkdtemp()
hashfile = os.path.relpath(os.path.join(tmpdir, 'GITVER.txt'))
print(hashfile) # prints something like '../../../../tmp/tmp82ywkodv/GITVER.txt'
with open(hashfile, 'w') as f :
    f.write(commithash)

setup(
        name='repro',
        data_files=[('repro', [hashfile])],
)

Start with the minimal setup.py reproducer and run both python setup.py install and python setup.py sdist in the reported Ubuntu/Python environment. Trace how the relative data_files path from the temporary directory is handled; done means sdist completes without the permission error while preserving the intended GITVER.txt packaging behavior.