Line 100 of setup/dist.py (in the code for this package), is: self.NUMERIC = 0 but should be: self.HAS_NUMERIC = 0 This causes the ebuild to break in some cases, when on line 107 of the same file, self.HAS_NUMERIC is accessed, but does not exist. Changing line 100, rezipping the tar.gz, and updating the hashes, solved this problem for me. The code for the package in the repository itself probably needs to be modified, though.
Fixed in portage. Thank you for reporting.