Godot: Missing .pck results in silent failure on Windows export

[voithos]

Godot version:
3.0.6

OS/device including version:
Window 10

Issue description:
I had exported a Godot game to Windows (from a Linux workstation), but in transferring the data I missed the .pck file. Attempting to start the .exe resulted in a brief "busy" indicator, and then... nothing.

At first, I thought Windows Defender was interfering, so I spent some time trying to figure that out, but I eventually realized that the .pck file was just missing. A simple error message would have saved me a bit of time.

Steps to reproduce: / Minimal reproduction project:
Should be (in theory) trivially reproducible with any project.

[Zireael07]

We recently had a very similar issue reported, where someone attempted to run a .exe without the .pck.

[Calinou]

It would make sense to call OS.alert() if the PCK file cannot be found when running an export template binary, since no command prompt will show up when running a release Windows export template (it will only display in debug mode).

[voithos]

Agreed with @Calinou. And I guess just to say it out loud - I only tried this on Windows, but we'd ideally want a missing .pck file to give some kind of error indication on all applicable platforms (I assume OS.alert() would do the right thing?).

[Calinou]

I only tried this on Windows, but we'd ideally want a missing .pck file to give some kind of error indication on all applicable platforms (I assume OS.alert() would do the right thing?).

OS.alert() works on all platforms — it will look different depending on the platform, but it should get the message across.