More cautious availablility checking for zarr remote access test.

Author: pp-mo

tests/integration/test_zarr_to_iris.py

@@ -7,6 +7,7 @@
 import iris
 import pytest
 import xarray as xr
+
 from ncdata.iris_xarray import cubes_from_xarray as conversion_func
 
 
@@ -88,7 +89,12 @@ def _is_url_ok(url):
     "https://uor-aces-o.s3-ext.jc.rl.ac.uk/"
     "esmvaltool-zarr/pr_Amon_CNRM-ESM2-1_02Kpd-11_r1i1p2f2_gr_200601-220112.zarr3"
 )
-_S3_accessible = _is_url_ok(S3_TEST_PATH)
+
+# Check 3 files, as we apparently sometimes get 'partial success'
+_S3_accessible = all(
+    _is_url_ok(S3_TEST_PATH + subpath)
+    for subpath in ["", "/.zattrs", "/.zmetadata"]
+)
 
 
 @pytest.mark.skipif(not _S3_accessible, reason="S3 url not accessible")