dev-lang/python: Fix py version ref for python_export in 2.7

dev-lang/python/python-2.7.10-r3.ebuild

@@ -314,7 +314,7 @@ src_install() {
 		vars=( PYTHON "${vars[@]}" )
 	fi
 
-	python_export "python${PYVER}" "${vars[@]}"
+	python_export "python${SLOT}" "${vars[@]}"
 	echo "EPYTHON='${EPYTHON}'" > epython.py || die
 	python_domodule epython.py
 }