Avoid deprecated Meson feature

* https://mesonbuild.com/Python-3-module.html

> This module is deprecated and replaced by the python module.

Author: cdunn2001

Diff for: .travis_scripts/meson_builder.sh

@@ -65,7 +65,7 @@ _COMPILER_NAME=`basename ${CXX}`
 _BUILD_DIR_NAME="build-${BUILD_TYPE}_${LIB_TYPE}_${_COMPILER_NAME}"
 
 ./.travis_scripts/run-clang-format.sh
-meson --buildtype ${BUILD_TYPE} --default-library ${LIB_TYPE} . "${_BUILD_DIR_NAME}"
+meson --fatal-meson-warnings --werror --buildtype ${BUILD_TYPE} --default-library ${LIB_TYPE} . "${_BUILD_DIR_NAME}"
 ninja -v -j 2 -C "${_BUILD_DIR_NAME}"
 
 cd "${_BUILD_DIR_NAME}"

Diff for: meson.build

@@ -71,8 +71,7 @@ jsoncpp_dep = declare_dependency(
   )
 
 # tests
-#python = import('python3').find_python()
-python = find_program('python3', 'python')
+python = import('python').find_installation()
 
 jsoncpp_test = executable(
   'jsoncpp_test',