Steps to repro:

1. Open Unity;
2. In the Launcher window click 'New' button;
3. Click 'Add Asset Package' button;
4. Select 'Gaia - Terrain Creation Texturing population';
5. Click 'Done';
6. Enter the name of the project, specify path and click 'Create Project'.

Expected result:
Package starts to decompress, and is eventually imported to the 'Assets' folder of the project.

Actual result:
- Decompressing doesn't happen;
- Editor throws error : Failed to import package with error: Couldn't decompress package.

See attached video and actual.png screenshot.
Regression introduced in 5.5.0b6.

Workaround is to import the package when launching Asset Store from Editor.

Notes:
- Reproducible in 5.6.0a1(trunk), 5.5.0b6;
- Not reproducible in 5.5.0b5, 5.5.0b4, 5.4.1p1;
- Reproducible only OSX 10.12; not reproducible in Windows 10;
- Happens only when importing package through Launcher; Not reproducible for importing packages inside active Editor window.