[libxml2] Add CI test for Python 3

[Nick Wellnhofer <nwellnhof src gnome org>]

commit 0ace6c4d7e92bd8637160860148aa8e5f660798a
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Thu Nov 19 17:35:11 2020 +0100

    Add CI test for Python 3

 .gitlab-ci.yml | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 801d4bcd..e145365a 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -10,7 +10,8 @@ default:
   #         curl git ca-certificates \
   #         autoconf automake libtool pkg-config \
   #         make gcc clang llvm \
-  #         python-dev zlib1g-dev liblzma-dev libgcrypt-dev \
+  #         zlib1g-dev liblzma-dev libgcrypt-dev \
+  #         python-dev python3-dev \
   #         cmake
   # WORKDIR /tests
   # RUN curl https://www.w3.org/XML/Test/xmlts20080827.tar.gz |tar xz
@@ -29,6 +30,12 @@ gcc:
   variables:
     CFLAGS: "-O2 -std=c89 -D_XOPEN_SOURCE=700"
 
+gcc:python3:
+  extends: .test
+  variables:
+    CONFIG: "--with-python=/usr/bin/python3"
+    CFLAGS: "-O2"
+
 clang:asan:
   extends: .test
   variables: