Index: Mk/Uses/python.mk
===================================================================
--- Mk/Uses/python.mk
+++ Mk/Uses/python.mk
@@ -247,6 +247,25 @@
 .endif
 
 # COMPAT KNOBS, remove them, once the tree is cleaned
+.undef _PY_COMPAT_OLD
+# We will reuse USE_PYTHON with a different meaning, so make sure that, while
+# we are in the transition phase from USE_PYTHON -> USES=python, it is mapped
+# and reassigned correctly
+.if defined(USE_PYTHON_BUILD) || defined(USE_PYTHON_RUN)
+# old style
+_PY_COMPAT_OLD=	yes
+.elif defined(USE_PYTHON)
+.if ${USE_PYTHON} == "yes" || ${USE_PYTHON} == "build" || \
+	${USE_PYTHON} == "run" || ${USE_PYTHON} == "2" || ${USE_PYTHON} == "3"
+# old style
+_PY_COMPAT_OLD=	yes
+.elif ${USE_PYTHON:tW:M*[1-9].[0-9]*} != ""
+# old style X.Y, X.Y+, X.Y-, -X.Y, X.Y-Z.A
+_PY_COMPAT_OLD=	yes
+.endif # ${USE_PYTHON} == "yes" ...
+.endif # defined(USE_PYTHON_BUILD) || defined(USE_PYTHON_RUN)
+
+.if defined(_PY_COMPAT_OLD)
 .if defined(USE_PYTHON)
 .if ${USE_PYTHON} != "yes"
 python_ARGS=	${USE_PYTHON}
@@ -260,31 +279,39 @@
 python_ARGS=	${USE_PYTHON_RUN},run
 .endif
 .endif # defined(USE_PYTHON)
-.if !defined(PYTHON_FEATURES)
-PYTHON_FEATURES=
+# Everything passed to python_ARGS, undef USE_PYTHON, since we will reuse
+# it with a different meaning below
+.undef USE_PYTHON
+.endif # defined(_PY_COMPAT_OLD)
+.undef _PY_COMPAT_OLD
+
+
+.if !defined(USE_PYTHON)
+USE_PYTHON=
 .if defined(USE_PYDISTUTILS)
-PYTHON_FEATURES+=	distutils
+USE_PYTHON+=	distutils
 .endif
+
 .if defined(PYDISTUTILS_AUTOPLIST)
-PYTHON_FEATURES+=	autoplist
+USE_PYTHON+=	autoplist
 .endif
 .if defined(PYTHON_PY3K_PLIST_HACK)
-PYTHON_FEATURES+=	py3kplist
+USE_PYTHON+=	py3kplist
 .endif
 .if defined(PYTHON_CONCURRENT_INSTALL)
-PYTHON_FEATURES+=	concurrent
+USE_PYTHON+=	concurrent
 .endif
 .if defined(USE_PYTHON_PREFIX)
-PYTHON_FEATURES+=	pythonprefix
+USE_PYTHON+=	pythonprefix
 .endif
 .if defined(PYDISTUTILS_NOEGGINFO)
-PYTHON_FEATURES+=	noegginfo
+USE_PYTHON+=	noegginfo
 .endif
-.endif # !defined(PYTHON_FEATURES)
+.endif # !defined(USE_PYTHON)
 # COMPAT KNOBS END
 
 # Make each individual feature available as _PYTHON_FEATURE_<FEATURENAME>
-.for var in ${PYTHON_FEATURES:S/,/ /g}
+.for var in ${USE_PYTHON:S/,/ /g}
 _PYTHON_FEATURE_${var:tu}=	yes
 .endfor