Stick to meson version 0.52.0. Version 0.53.0 has compatibility issues with python 3.5.2 which is shipped with Ubuntu 16.04. Better stick to a specific version and only update after checking compatibility. See mesonbuild/meson#6427.

.travis.yml

@@ -18,7 +18,7 @@ addons:
 
 before_script:
   - pip3 install wheel
-  - pip3 install meson
+  - pip3 install --upgrade 'meson==0.52.0'
   - meson --version
 
 script: