diff -urN /usr/ports/devel/scons/Makefile devel/scons/Makefile
--- /usr/ports/devel/scons/Makefile	2019-10-02 21:51:04.000000000 +0200
+++ devel/scons/Makefile	2019-10-24 14:11:17.031202000 +0200
@@ -14,8 +14,10 @@
 
 RUN_DEPENDS=	gm4:devel/m4
 
-USES=		python:2.7 shebangfix
+USES?=		python:2.7 shebangfix
 USE_PYTHON=	autoplist distutils
+
+CONFLICTS_INSTALL?=	scons-py3
 
 NO_ARCH=	yes