@koeppea the problem was this one.
Here you can see the build log
https://travis-ci.org/LocutusOfBorg/ettercap/builds/16365802

just try to revert this change, 
#include<ec_curses.h>
#include<ec_gtk.h>
without having HAVE_NCURSES and HAVE_GTK defined will fail with a "cannot find this file" failure.
this is because of cmake

   if (ENABLE_CURSES)
      include_directories( interfaces/curses interfaces/curses/widgets )
   endif (ENABLE_CURSES)
   if (ENABLE_GTK)
      include_directories( interfaces/gtk )
   endif(ENABLE_GTK)

that DOESN'T include them if they aren't built.