napari: Bundles on Mac and Windows build inconsistently

🐛 Bug

Bundles on Mac and Windows build inconsistently, seemingly due to some changes since 0.4.0, and occasionally display the following error:

The bundle cannot find the rcc.exe and/or pyside2-rcc.exe files despite these both existing in the bundle installation app-packages/pyside and app-packages/bin folders respectively. This does not happen if you have PySide installed in your base environment, or if you first run the napari bundle from an environment which does have PySide installed.

To Reproduce

Steps to reproduce the behavior:

1. Pull latest master
2. Ensure your base environment does not have PySide installed
3. Create a new environment with python=3.7 and pip
4. Run

python -m pip install briefcase==0.3.1 tomlkit wheel dmgbuild>=1.4.2
python -m pip install -e .[pyside2]
python bundle.py

1. Install the resulting .msi
2. Try to run napari from start menu.

Expected behavior

Bundle builds consistently regardless of what environments contain what packages on the build machine.

Additional context

This could potentially be fixed by:

• Pre-building resources in the bundling script
• Limiting the available paths when bundling e.g. not allowing the bundle to rely on anything outside of the napari installation folders
• Explicitly listing the relative paths of the rcc files?

This issue does not occur with the 0.4.0 release on Windows as far as I’m aware.