[bug#41022] [PATCH core-updates] gnu: python-gst: Fix build with Python 3.8.

[Christopher Baines]

Add a patch based on an upstream commit [1].

1: 10707f437f2fc3632067c6a0efa4432f7ebaf362

* gnu/packages/patches/python-gst-fix-build-with-python-3.8.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/gstreamer.scm (python-gst)[source]: Use the patch.
---
 gnu/local.mk                                  |  1 +
 gnu/packages/gstreamer.scm                    |  4 +-
 ...python-gst-fix-build-with-python-3.8.patch | 41 +++++++++++++++++++
 3 files changed, 45 insertions(+), 1 deletion(-)
 create mode 100644 
gnu/packages/patches/python-gst-fix-build-with-python-3.8.patch

diff --git a/gnu/local.mk b/gnu/local.mk
index 0111ae2161..acfc5cec4d 100644
--- a/gnu/local.mk
+++ b/gnu/local.mk
@@ -1394,6 +1394,7 @@ dist_patch_DATA =                                         
\
   %D%/packages/patches/python2-larch-coverage-4.0a6-compatibility.patch \
   %D%/packages/patches/python-configobj-setuptools.patch       \
   %D%/packages/patches/python-flask-restful-werkzeug-compat.patch      \
+  %D%/packages/patches/python-gst-fix-build-with-python-3.8.patch      \
   %D%/packages/patches/python-keras-integration-test.patch     \
   %D%/packages/patches/python-pep8-stdlib-tokenize-compat.patch \
   %D%/packages/patches/python-pyfakefs-remove-bad-test.patch   \
diff --git a/gnu/packages/gstreamer.scm b/gnu/packages/gstreamer.scm
index 93149e370e..7596796d68 100644
--- a/gnu/packages/gstreamer.scm
+++ b/gnu/packages/gstreamer.scm
@@ -521,7 +521,9 @@ non-linear editors.")
                     "gst-python-" version ".tar.xz"))
               (sha256
                (base32
-                "1a48ca66izmm8hnp608jv5isg3jxb0vlfmhns0bg9nbkilag7390"))))
+                "1a48ca66izmm8hnp608jv5isg3jxb0vlfmhns0bg9nbkilag7390"))
+              (patches
+               (search-patches "python-gst-fix-build-with-python-3.8.patch"))))
     (build-system meson-build-system)
     (arguments
      `(#:modules ((guix build meson-build-system)
diff --git a/gnu/packages/patches/python-gst-fix-build-with-python-3.8.patch 
b/gnu/packages/patches/python-gst-fix-build-with-python-3.8.patch
new file mode 100644
index 0000000000..49f41e0c03
--- /dev/null
+++ b/gnu/packages/patches/python-gst-fix-build-with-python-3.8.patch
@@ -0,0 +1,41 @@
+From 10707f437f2fc3632067c6a0efa4432f7ebaf362 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Sebastian=20Dr=C3=B6ge?= <address@hidden>
+Date: Fri, 13 Dec 2019 10:46:20 +0200
+Subject: [PATCH] Fix build with Python 3.8 by also checking for
+ python-3.X-embed.pc
+
+Since Python 3.8 the normal checks don't include the Python libraries
+anymore and linking of the gst-python module would fail.
+
+See also https://github.com/mesonbuild/meson/issues/5629
+
+Fixes https://gitlab.freedesktop.org/gstreamer/gst-python/issues/28
+---
+ meson.build | 11 +++++++++--
+ 1 file changed, 9 insertions(+), 2 deletions(-)
+
+diff --git a/meson.build b/meson.build
+index 5f13b48..d7c7e66 100644
+--- a/meson.build
++++ b/meson.build
+@@ -23,7 +23,17 @@ pygobject_dep = dependency('pygobject-3.0', fallback: 
['pygobject', 'pygobject_d
+ 
+ pymod = import('python')
+ python = pymod.find_installation(get_option('python'))
+-python_dep = python.dependency(required : true)
++pythonver = python.language_version()
++if pythonver.version_compare('<3.0')
++   error('Python2 is not supported anymore, please port your code to python3 
(@0@ specified)'.format(python.language_version()))
++endif
++
++# Workaround for https://github.com/mesonbuild/meson/issues/5629
++# https://gitlab.freedesktop.org/gstreamer/gst-python/issues/28
++python_dep = dependency('python-@0@-embed'.format(pythonver), version: '>=3', 
required: false)
++if not python_dep.found()
++  python_dep = python.dependency(required : true)
++endif
+ 
+ python_abi_flags = python.get_variable('ABIFLAGS', '')
+ pylib_loc = get_option('libpython-dir')
+-- 
+2.26.2
-- 
2.26.0