Update version of meson.

We should not force a specific version as it is a environment problem,
but for now, set it.

.travis.yml

@@ -114,7 +114,7 @@ env:
   global:
     - NIGHTLY_DATE=$(date +%Y-%m-%d)
     - SSH_KEY=/tmp/private/travisci_builder_id_key
-    - DOCKER_VERSION=2
+    - DOCKER_VERSION=4
   matrix:
     - PLATFORM="flatpak" DESKTOP_ONLY=1
     - PLATFORM="native_dyn"

setup.py

@@ -35,7 +35,7 @@ setup(
     packages=find_packages(),
     include_package_data=True,
     install_requires=[
-        'meson==0.49.2'
+        'meson==0.52.1'
     ],
     entry_points={
         'console_scripts': [

travis/xenial_builder.dockerfile

@@ -20,7 +20,9 @@ RUN apt update -q && \
 #    vim less grep \
   && \
   apt-get clean -y && \
-  rm -rf /var/lib/apt/lists/* /usr/share/doc/* /var/cache/debconf/*
+  rm -rf /var/lib/apt/lists/* /usr/share/doc/* /var/cache/debconf/* && \
+  pip3 install --upgrade pip && \
+  pip3 install meson==0.52.1 pytest gcovr
 
 # Create user
 RUN useradd --create-home ci_builder
@@ -32,4 +34,4 @@ ENV TRAVIS_BUILD_DIR /home/ci_builder/kiwix-build
 ENV GRADLE_USER_HOME /home/ci_builder
 ENV TRAVIS_OS_NAME linux_xenial
 
-CMD pip3 install --user ./kiwix-build && kiwix-build/travis/compile_all.py
+CMD pip3 install --user --no-deps ./kiwix-build && kiwix-build/travis/compile_all.py