Please describe the problem.

      retrieveKeyFile:                                  FAIL
          Exception: .git\annex\objects\fc0\296\SHA256E-s1048576--c347f274df214671e3bebb6674cc5d2e6c226d8358a416859d5fc3c79a08eb1f.this-is-a-test-key\SHA256E-s1048576--c347f274df214671e3bebb6674cc5d2e6c226d8358a416859d5fc3c79a08eb1f.this-is-a-test-key: DeleteFile "\\\\?\\C:\\Users\\runneradmin\\.t\\main2\\.git\\annex\\objects\\fc0\\296\\SHA256E-s1048576--c347f274df214671e3bebb6674cc5d2e6c226d8358a416859d5fc3c79a08eb1f.this-is-a-test-key\\SHA256E-s1048576--c347f274df214671e3bebb6674cc5d2e6c226d8358a416859d5fc3c79a08eb1f.this-is-a-test-key": permission denied (Access is denied.)
        fsck downloaded object:                           OK (0.01s)
        retrieveKeyFile resume from 33%:                  FAIL
          Exception: .git\annex\tmp\SHA256E-s1048576--c347f274df214671e3bebb6674cc5d2e6c226d8358a416859d5fc3c79a08eb1f.this-is-a-test-key: openBinaryFile: permission denied (Permission denied)
        fsck downloaded object:                           OK (0.01s)
        retrieveKeyFile resume from 0:                    FAIL
          Exception: .git\annex\tmp\SHA256E-s1048576--c347f274df214671e3bebb6674cc5d2e6c226d8358a416859d5fc3c79a08eb1f.this-is-a-test-key: openFile: permission denied (Permission denied)
        fsck downloaded object:                           OK (0.01s)
cp: cannot create regular file '.git\annex\tmp\SHA256E-s1048576--c347f274df214671e3bebb6674cc5d2e6c226d8358a416859d5fc3c79a08eb1f.this-is-a-test-key': Permission denied
        retrieveKeyFile resume from end:                  FAIL
          Exception: .git\annex\objects\fc0\296\SHA256E-s1048576--c347f274df214671e3bebb6674cc5d2e6c226d8358a416859d5fc3c79a08eb1f.this-is-a-test-key\SHA256E-s1048576--c347f274df214671e3bebb6674cc5d2e6c226d8358a416859d5fc3c79a08eb1f.this-is-a-test-key: DeleteFile "\\\\?\\C:\\Users\\runneradmin\\.t\\main2\\.git\\annex\\objects\\fc0\\296\\SHA256E-s1048576--c347f274df214671e3bebb6674cc5d2e6c226d8358a416859d5fc3c79a08eb1f.this-is-a-test-key\\SHA256E-s1048576--c347f274df214671e3bebb6674cc5d2e6c226d8358a416859d5fc3c79a08eb1f.this-is-a-test-key": permission denied (Access is denied.)
        fsck downloaded object:                           OK (0.01s)
        removeKey when present:                           OK (0.09s)

I think this fail is relatively recent since 5 days ago is green for git-annex (but red for datalad). Overall today's log for 8.20210331-ge3de27dcc says 126 out of 833 tests failed (599.24s)

not sure if relates to ubuntu build fails which seems to be less wild, so filing separately

Fixed by disabling the failing tests on windows, see comments for the gory details. done --Joey