fix: improve test so that it raises at the right point [skip ds005][skip ds054][skip ds210][skip tests]

before this change, tests would break because templateflow attempts to
use home first, and the docker run command would have mounted it with
readonly.

now this is implemented separately, and a safe new $HOME mocked.

Close #1777.

Author: oesteban

.circleci/config.yml

@@ -226,7 +226,7 @@ jobs:
           no_output_timeout: 2h
           command: |
             docker run -ti --rm=false \
-              -e TEST_READONLY_FILESYSTEM=1 -v $HOME:/home/fmriprep:ro \
+              -e TEST_READONLY_FILESYSTEM=1 -v $HOME:/home/readonly:ro \
               --entrypoint="pytest" poldracklab/fmriprep:latest \
               /src/fmriprep/fmriprep -svx --doctest-modules
 

fmriprep/cli/tests/test_version.py

@@ -166,16 +166,17 @@ def mock_get(*args, **kwargs):
 
 def test_readonly(tmp_path, monkeypatch):
     """Test behavior when $HOME/.cache/fmriprep/latest can't be written out."""
-    if getenv('TEST_READONLY_FILESYSTEM'):
-        cachedir = Path(getenv('HOME')) / '.cache'
-    else:
-        monkeypatch.setenv('HOME', str(tmp_path))
-        cachedir = tmp_path / '.cache'
+    home_path = Path('/home/readonly') if getenv('TEST_READONLY_FILESYSTEM') \
+        else tmp_path
+    monkeypatch.setenv('HOME', str(home_path))
+    cachedir = home_path / '.cache'
+
+    if getenv('TEST_READONLY_FILESYSTEM') is None:
         cachedir.mkdir(mode=0o555, exist_ok=True)
 
     # Make sure creating the folder will raise the exception.
     with pytest.raises(OSError):
-        (cachedir / 'fmriprep').mkdir()
+        (cachedir / 'fmriprep').mkdir(parents=True)
 
     # Should not raise
     check_latest()