| ## python.find_installation() now accepts pure argument | |
| The default value of `pure:` for `py.install_sources()` and | |
| `py.get_install_dir()` can now be changed by explicitly passing a `pure:` kwarg | |
| to `find_installation()`. | |
| This can be used to ensure that multiple `install_sources()` invocations do not | |
| forget to specify the kwarg each time. |