extopenscad doesn't set returncode properly when errors are produced during runtime

running this ESCAD script:
```
bogus_command(d=100);
```
with this command:
`$ extopenscad test.escad -o test.stl && echo "last command worked!"`

produces:
```
Loading File.
Processing File.
No objects to render.
Error at line 1, column 1: Module bogus_command not in scope.
last command worked!
```

where the last line `last command worked!` is unexpected and feels like incorrect behavior.