Created attachment 302723 [details] emerge --info output in my box, grib_api-1.9.9.ebuild installs python module into dir: '/usr/lib64/python2.7/site-packages/grib_api/', and if you try to 'import gribapi', python will failed to find the gribapi module, unless you set PYTHONPATH manually.
fixed in 1.9.9-r1. thanks!