icons,vaadin,font-awesome,vaadin-valo-theme
We changed the Java version of the project form 1.7 to 1.6. That solved the problem.
Preferred way is to edit Valo theme Sass variables, its easy and detailed info can be found in this Vaadin wiki article. Basically you make your custom theme which inherits from vaadin Valo theme and override only variables you are interested in. So you can override only variable for font...