Hydra fails with a `DirectoryError: [Errno 21] Is a directory: '/build/source/fsspec/tests/__pycache__'`.
I suspect that both drvs `python37Packages.fsspec` and `python38Packages.fsspec` share the same folder
`'/build/source/fsspec/tests/__pycache__'` which leads to problems. To fix it I just let each drvs run in a
tmp directory using `pytestFlagsArray = [ "--rootdir=$(mktemp -d)" ];`.
Disables the `test_touch` test which fails with the following assertion error on hydra darwin only:
```
tmpdir = local('/private/tmp/nix-build-python3.8-fsspec-0.8.3.drv-0/pytest-of-nixbld3/pytest-0/test_touch0')
def test_touch(tmpdir):
import time
fn = tmpdir + "/in/file"
fs = fsspec.filesystem("file", auto_mkdir=False)
with pytest.raises(OSError):
fs.touch(fn)
fs = fsspec.filesystem("file", auto_mkdir=True)
fs.touch(fn)
info = fs.info(fn)
time.sleep(0.2)
fs.touch(fn)
info2 = fs.info(fn)
if not WIN:
> assert info2["mtime"] > info["mtime"]
E assert 1601358357.0 > 1601358357.0
fsspec/implementations/tests/test_local.py:322: AssertionError
```
