The problem
I was trying to install dev-util/subversion but emerge failed when java-config was called.
The output:
Traceback (most recent call last):
File "/usr/bin/java-config-2", line 8, in <module>
from java_config_2 import __version__
ImportError: No module named java_config_2</span>
Possible solution
python-updater was not executed after a python upgrade so run it now:
# python-updater -iv