Steps to reproduce:

1. Create new project
2. Log something to console
3. Select text (see attached Console.png)
4. Copy using keyboard shortcut ctrl + c
5. Try to paste it somewhere (notepad etc.) and notice that text did not get copied

Note: Another way which doesn't require logging to console is opening About Unity and trying to copy version using keyboard shortcut

Tested on Windows 10
Reproduced with: 2018.3.0a6 (da73f99a4e02)
Not reproducible: 2018.3.0a5