fix support for osx

[jaimergp]

This PR adds the minimum amount of changes needed to make OSX applications work again. It's not the most elegant code, but let's start small.

Summary of changes:

• Recover utils.get_executable from the original appinst
• Fix class signatures
• Conform to the menuinst.install(...) API expected by conda (same as windows)
• Comply with the modern plistlib API
• Slugify script name (last component of/Applications/${NAME}.app/Contents/MacOS/${NAME})
• Bring some placeholders used on Windows too

[jaimergp]

This will need changes in the menuinst recipe too. The current implementation requires python.app for some reason.

[hoechenberger]

I'd just like to say that it would be great to have these changes added to menuinst. If there's any way in which I could help make that happen, please do let me know.

[isuruf]

This looks good to me. Can we enable tests for this so that we don't accidentally break this in the future?

[jaimergp]

Thanks @isuruf! I don't know if we want to pursue this series of updates though (this PR, and the one for Linux).

There's a full rewrite on #91 that implements the same functionality with a new cross-platform schema. It could be considered a new major version, though.

Enabling non-Windows also requires changes in conda itself.

I think we should close this PR, and #89, and work our way towards cross-platform compatibility through #91.

[hoechenberger]

I think we should close this PR, and #89, and work our way towards cross-platform compatibility through #91.

I agree!