dev-python/mpi4py: enable py3.10

Signed-off-by: Arthur Zamarin <arthurzam@gentoo.org>

dev-python/mpi4py/mpi4py-3.0.3.ebuild

@@ -1,9 +1,9 @@
-# Copyright 1999-2020 Gentoo Authors
+# Copyright 1999-2021 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
 EAPI=7
 
-PYTHON_COMPAT=( python3_{7,8,9} )
+PYTHON_COMPAT=( python3_{8..10} )
 inherit distutils-r1
 
 DESCRIPTION="Message Passing Interface for Python"
@@ -36,6 +36,13 @@ PATCHES=(
 	"${FILESDIR}/${P}-py38futures.patch"
 )
 
+src_prepare() {
+	sed -e 's/++Py_REFCNT/Py_INCREF/' \
+		-e 's/--Py_REFCNT/Py_DECREF/' \
+		-i src/*.c || die
+	distutils-r1_src_prepare
+}
+
 python_prepare_all() {
 	# not needed on install
 	rm -vr docs/source || die