Reproduction steps:
1. Create a new project.
2.1. Press Menu/Assets/Reimport All.
Or
2.2. Open player settings and change API Compatibility Level.
Or
2.3.. Other situation that requires Unity restart.

Expected result: Unity will be restarted.
Actual result: Unity closes.

Reproduced on: 2017.2.0b2, 2017.2.0b3.
Works fine: 2017.2.0b1
Regression introduced in 2017.2.0b2.

Notes: Make sure there is no other Unity opened. Restart seems to work fine when earlier versions of Unity are launched as well.

Reproduced on Windows 10.
Works fine on Linux and Mac.