After updating dev-python/sip to 4.9.3, rebuilding dev-python/pyqwt failed.
Created attachment 211185 [details] build.log build log of dev-python/pyqwt-5.1.0
Created attachment 211187 [details] emerge --info =dev-python/pyqwt-5.1.0
5.2.0 does not have problem with newer sip
Fixed. Thanks for reporting!