I recently submitted PR #10532. This PR makes no apparent changes that could affect the FileSystem tests. However, the functional test suites all failed with problems related to "FileSystem - raw" tests. See https://dev.azure.com/ms/vscode-python/_build/results?buildId=67939&view=logs&j=a3970498-841d-5222-305d-7944b537959f&t=1125c8d9-7d61-50ff-e942-302286e57067 for an example.