[Test] Skip conversion tests if no Python package is being built

Converting between different mechanism formats require at least
the "minimal" Python package to be built.

test/SConscript

@@ -96,6 +96,8 @@ def addTestProgram(subdir, progName, env_vars={}):
     testenv['ENV'].update(env_vars)
     if env["skip_slow_tests"]:
         testenv.Append(CPPDEFINES=["CT_SKIP_SLOW"])
+    if env["python_package"] == "none":
+        testenv.Append(CPPDEFINES=["CT_NO_PYTHON"])
     program = testenv.Program(pjoin(subdir, progName),
                               multi_glob(testenv, subdir, 'cpp'))
     passedFile = File(pjoin(str(program[0].dir), '%s.passed' % program[0].name))