meld:master commits

Without this you get nothing when it fails.

Tests are just run with `pytest` now.

Fix suggested by @Arnaudv6

Attempt to fix CI installing packages to the system python See merge request !142

This is just a theory, but it looks like pip was removed from the default python install, which meant that the pip that was used for our python package install below came from the system python install, which then meant that the subsequent pyinstaller build couldn't find it.