1. What happened
Failed to upgrade A$ package https://www.assetstore.unity3d.com/en/#!/content/52103 (AQUAS Water/River Set) from 5.6.2p2 to 2017.2.0b2. During API upgrade, the message box 'Opening file failed... Force Quit/Cancel/Try Again' appears (see attachhed). 'Cancel' or 'Try Again' doesn't solve the issue.
Error doesn't occur if upgrading from 2017.1, or importing the package into 2017.2 directly.

2. How we can reproduce it using the example you attached
The project, probably, already in a broken state.
To repro again:
- Import the project (AQUAS Water/River Set) into new project in 5.6
- Agree to API upgrade and close Editor after the upgrade completion
- Open the project in 2017.2
>>> It has warnings in Console, and error '...WebPlayer is obsolete...'.
- Click the error to open the code in IDE
- Delete the offending 'case' statement (CrossPlatformInputInitialize.cs, line 91) and Save
- Return to Editor
>>> It'll start updating the API and will hang shortly

User is unable now to open the project with this version of Editor.

The upgrade works fine from 5.6 to 2017.1.