tmpdir path too long on macOS

I have a unit test that runs gpg. First we set GNUPGHOME to the temporary directory that pytest creates, then we run it using our own keys. However, gpg fails with the following error:

gpg: keybox '/private/var/folders/21/hwq39zyj4g36x6zjfyl5l8080000gn/T/pytest-of-Adam/pytest-5/test_buildcache0/gpg/pubring.kbx' created
gpg: can't connect to the agent: File name too long
gpg: agent_genkey failed: No agent running
gpg: key generation failed: No agent running

According to https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=847206, gpg cannot handle long paths. Is there any way to shorten /private/var/folders/21/hwq39zyj4g36x6zjfyl5l8080000gn/T/pytest-of-Adam/pytest-5/test_buildcache0/gpg/pubring.kbx?

platform darwin – Python 3.7.3, pytest-3.2.5, py-1.4.34, pluggy-0.4.0

Possibly related to #291

[The-Compiler]

You can configure any command line option in the config via addopts.

[The-Compiler]

FWIW I have this in my testsuite for a similar issue:

@pytest.fixture()
def short_tmpdir():
    with tempfile.TemporaryDirectory() as tdir:
        yield py.path.local(tdir)