multi-root workspace settings for `python.pythonPath` not work

[lihuanshuai]

Environment data

VS Code version: vscode 1.19.3
Python Extension version: 2018.1.0
Python Version: 2.7.13
OS and version: macOS 10.13.3

Actual behavior

I am using multi-root workspace when doing some work on several Python projects. Each project has virtual env for due to different dependencies. So I set "python.pythonPath": "${workspaceFolder}/venv/bin/python" in workspace setting. but, no matter which file is opened, Python interpreter is always venv/bin/python under first folder of workspace.

Expected behavior

Python interpreter shall be venv/bin/python under current folder of workspace.

Steps to reproduce:

• Create folders with python files and venv
• Add them to workspace, save workspace to .code-workspace file, close workspace and reopen

Logs

[DonJayamanne]

Duplicate of #690