gnu: python-libxml2: Fix building with python-3.9.

* gnu/packages/xml.scm (python-libxml2)[source]: Add patch.
* gnu/packages/patches/python-libxml2-python39-compat.patch: New file.
* gnu/local.mk (dist_patch_DATA): Register it.

gnu/local.mk

@@ -1520,6 +1520,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/python-pep8-stdlib-tokenize-compat.patch \
   %D%/packages/patches/python-pyfakefs-remove-bad-test.patch	\
   %D%/packages/patches/python-flint-includes.patch		\
+  %D%/packages/patches/python-libxml2-python39-compat.patch	\
   %D%/packages/patches/python-libxml2-utf8.patch		\
   %D%/packages/patches/python-memcached-syntax-warnings.patch	\
   %D%/packages/patches/python-mox3-python3.6-compat.patch	\

gnu/packages/patches/python-libxml2-python39-compat.patch

@@ -0,0 +1,94 @@
+https://gitlab.gnome.org/GNOME/libxml2/-/commit/e4fb36841800038c289997432ca547c9bfef9db1.patch
+
+From e4fb36841800038c289997432ca547c9bfef9db1 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Miro=20Hron=C4=8Dok?= <miro@hroncok.cz>
+Date: Fri, 28 Feb 2020 12:48:14 +0100
+Subject: [PATCH] Parenthesize Py<type>_Check() in ifs
+
+In C, if expressions should be parenthesized.
+PyLong_Check, PyUnicode_Check etc. happened to expand to a parenthesized
+expression before, but that's not API to rely on.
+
+Since Python 3.9.0a4 it needs to be parenthesized explicitly.
+
+Fixes https://gitlab.gnome.org/GNOME/libxml2/issues/149
+---
+ python/libxml.c |  4 ++--
+ python/types.c  | 12 ++++++------
+ 2 files changed, 8 insertions(+), 8 deletions(-)
+
+diff --git a/python/libxml.c b/python/libxml.c
+index bc676c4e..81e709f3 100644
+--- a/python/libxml.c
++++ b/python/libxml.c
+@@ -294,7 +294,7 @@ xmlPythonFileReadRaw (void * context, char * buffer, int len) {
+ 	lenread = PyBytes_Size(ret);
+ 	data = PyBytes_AsString(ret);
+ #ifdef PyUnicode_Check
+-    } else if PyUnicode_Check (ret) {
++    } else if (PyUnicode_Check (ret)) {
+ #if PY_VERSION_HEX >= 0x03030000
+         Py_ssize_t size;
+ 	const char *tmp;
+@@ -359,7 +359,7 @@ xmlPythonFileRead (void * context, char * buffer, int len) {
+ 	lenread = PyBytes_Size(ret);
+ 	data = PyBytes_AsString(ret);
+ #ifdef PyUnicode_Check
+-    } else if PyUnicode_Check (ret) {
++    } else if (PyUnicode_Check (ret)) {
+ #if PY_VERSION_HEX >= 0x03030000
+         Py_ssize_t size;
+ 	const char *tmp;
+diff --git a/python/types.c b/python/types.c
+index c2bafeb1..ed284ec7 100644
+--- a/python/types.c
++++ b/python/types.c
+@@ -602,16 +602,16 @@ libxml_xmlXPathObjectPtrConvert(PyObject *obj)
+     if (obj == NULL) {
+         return (NULL);
+     }
+-    if PyFloat_Check (obj) {
++    if (PyFloat_Check (obj)) {
+         ret = xmlXPathNewFloat((double) PyFloat_AS_DOUBLE(obj));
+-    } else if PyLong_Check(obj) {
++    } else if (PyLong_Check(obj)) {
+ #ifdef PyLong_AS_LONG
+         ret = xmlXPathNewFloat((double) PyLong_AS_LONG(obj));
+ #else
+         ret = xmlXPathNewFloat((double) PyInt_AS_LONG(obj));
+ #endif
+ #ifdef PyBool_Check
+-    } else if PyBool_Check (obj) {
++    } else if (PyBool_Check (obj)) {
+ 
+         if (obj == Py_True) {
+           ret = xmlXPathNewBoolean(1);
+@@ -620,14 +620,14 @@ libxml_xmlXPathObjectPtrConvert(PyObject *obj)
+           ret = xmlXPathNewBoolean(0);
+         }
+ #endif
+-    } else if PyBytes_Check (obj) {
++    } else if (PyBytes_Check (obj)) {
+         xmlChar *str;
+ 
+         str = xmlStrndup((const xmlChar *) PyBytes_AS_STRING(obj),
+                          PyBytes_GET_SIZE(obj));
+         ret = xmlXPathWrapString(str);
+ #ifdef PyUnicode_Check
+-    } else if PyUnicode_Check (obj) {
++    } else if (PyUnicode_Check (obj)) {
+ #if PY_VERSION_HEX >= 0x03030000
+         xmlChar *str;
+ 	const char *tmp;
+@@ -650,7 +650,7 @@ libxml_xmlXPathObjectPtrConvert(PyObject *obj)
+ 	ret = xmlXPathWrapString(str);
+ #endif
+ #endif
+-    } else if PyList_Check (obj) {
++    } else if (PyList_Check (obj)) {
+         int i;
+         PyObject *node;
+         xmlNodePtr cur;
+-- 
+GitLab
+

gnu/packages/xml.scm

@@ -5,7 +5,7 @@
 ;;; Copyright © 2015 Sou Bunnbu <iyzsong@gmail.com>
 ;;; Copyright © 2015, 2016, 2017, 2018, 2020 Ricardo Wurmus <rekado@elephly.net>
 ;;; Copyright © 2015, 2016, 2017 Mark H Weaver <mhw@netris.org>
-;;; Copyright © 2015, 2016, 2017, 2018, 2020 Efraim Flashner <efraim@flashner.co.il>
+;;; Copyright © 2015, 2016, 2017, 2018, 2020, 2021 Efraim Flashner <efraim@flashner.co.il>
 ;;; Copyright © 2015 Raimon Grau <raimonster@gmail.com>
 ;;; Copyright © 2016 Mathieu Lirzin <mthl@gnu.org>
 ;;; Copyright © 2016, 2017 Leo Famulari <leo@famulari.name>
@@ -297,8 +297,10 @@ (define-public python-libxml2
     (name "python-libxml2")
     (source (origin
               (inherit (package-source libxml2))
-              (patches (cons (search-patch "python-libxml2-utf8.patch")
+              (patches
-                             (origin-patches (package-source libxml2))))))
+                (append (search-patches "python-libxml2-python39-compat.patch"
+                                        "python-libxml2-utf8.patch")
+                        (origin-patches (package-source libxml2))))))
     (build-system python-build-system)
     (outputs '("out"))
     (arguments