Generate fixture for zarr-developers#1312 if it is missing

This is a temporary fix for the larger issue of out-of-tree
testing described in zarr-developers#1347, but this should allow a release
of 2.14.1 which passes on conda.

zarr/tests/test_attrs.py

@@ -1,7 +1,9 @@
 import json
 
+import pathlib
 import pytest
 
+import zarr
 from zarr._storage.store import meta_root
 from zarr.attrs import Attributes
 from zarr.storage import KVStore, DirectoryStore
@@ -50,6 +52,16 @@ def test_storage(self, zarr_version):
 
     def test_utf8_encoding(self, zarr_version):
 
+        project_root = pathlib.Path(zarr.__file__).resolve().parent.parent
+        fixdir = project_root / "fixture" / "utf8attrs"
+        if not fixdir.exists():  # pragma: no cover
+            # store the data - should be one-time operation
+            fixdir.mkdir()
+            with (fixdir / ".zattrs").open("w", encoding="utf-8") as f:
+                f.write('{"foo": "た"}')
+            with (fixdir / ".zgroup").open("w", encoding="utf-8") as f:
+                f.write("""{\n    "zarr_format": 2\n}""")
+
         # fixture data
         fixture = group(store=DirectoryStore('fixture'))
         assert fixture['utf8attrs'].attrs.asdict() == dict(foo='た')