[gentoo-user] setuptools (python) - how to disable the sandbox ?

[Helmut Jarausch]

Hi,
I want to create an ebuild for a package that's not in the tree  
(http://pypi.python.org/pypi/grako)

Unfortunately, this always fails due to

   File "/usr/lib64/python3.6/site-packages/setuptools/sandbox.py",  
line 411, in _violation
     raise SandboxViolation(operation, args, kw)
setuptools.sandbox.SandboxViolation: SandboxViolation:  
open('/var/tmp/portage/dev-python/grako-3.99.9/work/grako-3.99.9-python3_6/lib/ptr.py',  
'wb') {}

I wouldn't mind the package to write to its own working directory  
/var/tmp/portage/dev-python/grako-3.99.9/work
but I cannot find out how to disable setuptools.sandbox

I've tried addwrite "$S" and FEATURES=-usersandbox  -sandbox

but nothing helps.

Many thanks for a hint,
Helmut