I have python2.7, python3.4, python3.5 and python3.6 installed (I'm a developer). I have PYTHON_SINGLE_TARGET="python3_4" and PYTHON_TARGETS="python2_7 python3_4 python3_5 python3_6" in make.conf.

When trying to install cura with these settings, it will fail to build with an error about not finding an interpreter with at least version 3.5.

If I change to PYTHON_SINGLE_TARGET="python3_5" for media-gfx/cura, dev-python/libarcus and dev-python/uranium, it will build, but when trying to run cura it will fail with a missing module:

╼ cura
Traceback (most recent call last):
  File "/usr/bin/cura", line 9, in <module>
    from UM.Platform import Platform
ImportError: No module named 'UM'

I did a quick change to /usr/bin/cura changing from python3 to python3.5, but then I get a different error instead:

 cura
An uncaught exception has occurred!
Traceback (most recent call last):
  File "/usr/bin/cura", line 53, in <module>
    import cura.CuraApplication
  File "/usr/lib64/python3.5/site-packages/cura/CuraApplication.py", line 27, in <module>
    from UM.Workspace.WorkspaceReader import WorkspaceReader
ImportError: No module named 'UM.Workspace'

There is something wrong with the dependencies and USE-flags here, and also the installed binary seems to be making assumptions that aren't right.

Attached output of emerge --info, and the contents of /etc/portage/package.use/cura.