Force make to stop if Python not found

Author: dnpwwo

.travis.yml

@@ -16,6 +16,7 @@ sources:
 
 # What to install before the build
 before_install:
+  - cmake --version
   # Domoticz needs the full history to be able to calculate the version string
   - git fetch --unshallow
   # OpenZWave

CMakeLists.txt

@@ -63,7 +63,7 @@ ENDIF(USE_BUILTIN_SQLITE)
 
 option(USE_PYTHON_PLUGINS "Use Python Plugins" YES)
 IF(USE_PYTHON_PLUGINS)
-  find_package(PythonLibs 3.4.0)
+  find_package(PythonLibs 3.4.0 REQUIRED)
   IF(PYTHONLIBS_FOUND)
     MESSAGE(STATUS "Python3 includes found at: ${PYTHON_INCLUDE_PATH}")
     INCLUDE_DIRECTORIES(${PYTHON_INCLUDE_PATH})