Detect invalid collectors.

The program would blow up anyway, but provide users with a more friendly
error message.

Change-Id: If70fc27b61963058af036568b88535b7f2dcff3f

os_collect_config/collect.py

@@ -106,8 +106,15 @@ def collect_all(collectors, store=False, requests_impl_map=None):
 def __main__(args=sys.argv, requests_impl_map=None):
     setup_conf()
     CONF(args=args[1:], prog="os-collect-config")
+
     log.setup("os-collect-config")
 
+    unknown_collectors = set(CONF.collectors) - set(DEFAULT_COLLECTORS)
+    if unknown_collectors:
+        raise exc.InvalidArguments(
+            'Unknown collectors %s. Valid collectors are: %s' %
+            (list(unknown_collectors), DEFAULT_COLLECTORS))
+
     (any_changed, content) = collect_all(cfg.CONF.collectors,
                                          store=bool(CONF.command),
                                          requests_impl_map=requests_impl_map)

os_collect_config/exc.py

@@ -16,3 +16,7 @@ class CfnMetadataNotConfigured(SourceNotAvailable):
 
 class HeatLocalMetadataNotAvailable(SourceNotAvailable):
     """The local Heat metadata is not available."""
+
+
+class InvalidArguments(ValueError):
+    """Invalid arguments."""

os_collect_config/tests/test_collect.py

@@ -24,6 +24,7 @@ import testtools
 from testtools import matchers
 
 from os_collect_config import collect
+from os_collect_config import exc
 from os_collect_config.tests import test_cfn
 from os_collect_config.tests import test_ec2
 from os_collect_config.tests import test_heat_local
@@ -126,6 +127,10 @@ class TestCollect(testtools.TestCase):
         self.assertIn('ec2', out_struct)
         self.assertIn('cfn', out_struct)
 
+    def test_main_invalid_collector(self):
+        fake_args = ['os-collect-config', 'invalid']
+        self.assertRaises(exc.InvalidArguments, self._call_main, fake_args)
+
 
 class TestCollectAll(testtools.TestCase):
     def setUp(self):