[testing] separate import test for ddg4 and rest of dd4hep

This avoids a test failure when DD4hep is built with
DD4HEP_USE_GEANT4=OFF

DDTest/CMakeLists.txt

@@ -51,6 +51,11 @@ ADD_TEST( t_test_python_import "${CMAKE_INSTALL_PREFIX}/bin/run_test.sh"
 SET_TESTS_PROPERTIES( t_test_python_import PROPERTIES FAIL_REGULAR_EXPRESSION  "Exception;EXCEPTION;ERROR;Error" )
 
 if (DD4HEP_USE_GEANT4)
+
+  ADD_TEST( t_test_python_import_ddg4 "${CMAKE_INSTALL_PREFIX}/bin/run_test.sh"
+    pytest ${PROJECT_SOURCE_DIR}/DDTest/python/test_import_ddg4.py)
+  SET_TESTS_PROPERTIES( t_test_python_import_ddg4 PROPERTIES FAIL_REGULAR_EXPRESSION  "Exception;EXCEPTION;ERROR;Error" )
+
   foreach(TEST_NAME
       test_EventReaders
       )

DDTest/python/test_import.py

 #!/usr/bin/env python
 """
-Some imports to make sure that the DD4hep environment is complete
+Some imports to make sure that the DD4hep environment is complete.
+Since it can be disabled in CMake, the import of DDG4 is tested in another file.
 """
 from __future__ import absolute_import, unicode_literals, print_function
 import traceback
@@ -11,7 +12,6 @@ parametrize = pytest.mark.parametrize
 
 moduleNames = [
     'dd4hep',
-    'DDG4',
     'DDRec',
     'DDDigi',
     ]

DDTest/python/test_import_ddg4.py

+#!/usr/bin/env python
+"""
+Some imports to make sure that the DD4hep environment is complete.
+This file adds a test for the DDG4 python module.
+"""
+
+from __future__ import absolute_import
+from test_import import test_module, parametrize
+
+
+moduleNames = [
+    'DDG4',
+    ]
+
+
+@parametrize('moduleName', moduleNames)
+def test_module_ddg4(moduleName):
+    test_module(moduleName)