validate:launcher: Report error and exit when a testsuite could not load

Otherwise the user might end up seeing a lot of meaningless logs about
'removed' tests.

validate/launcher/baseclasses.py

@@ -1210,6 +1210,7 @@ class _TestsLauncher(Loggable):
                 printc("Could not load testsuite: %s"
                        " maybe because of missing TestManager"
                        % (testsuite), Colors.FAIL)
+                return False
 
     def _load_config(self, options):
         printc("Loading config files is DEPRECATED"
@@ -1250,7 +1251,9 @@ class _TestsLauncher(Loggable):
             tester.set_settings(options, args, self.reporter)
 
         if not options.config and options.testsuites:
-            self._setup_testsuites()
+            if self._setup_testsuites() is False:
+                return False
+        return True
 
     def _check_tester_has_other_testsuite(self, testsuite, tester):
         if tester.name != testsuite.TEST_MANAGER[0]:

validate/launcher/main.py

@@ -525,7 +525,8 @@ Note that all testsuite should be inside python modules, so the directory should
 
     # Ensure that the scenario manager singleton is ready to be used
     ScenarioManager().config = options
-    tests_launcher.set_settings(options, [])
+    if not tests_launcher.set_settings(options, []):
+        exit(1)
     if tests_launcher.list_tests() == -1:
         printc("\nFailling as tests have been removed/added "
                " (--fail-on-testlist-change)", Colors.FAIL)