Don't threat as an error when OS_CLOUD env variable is not defined.

Change-Id: Ib9b8278e099d4227d738c368ab55bcbb6f8c0542

tobiko/openstack/keystone/_clouds_file.py

@@ -95,6 +95,9 @@ class CloudsFileKeystoneCredentialsFixture(
 
     def get_credentials(self):
         cloud_name = self._get_cloud_name()
+        if cloud_name is None:
+            return None
+
         clouds_content = self._get_clouds_content()
         clouds_section = clouds_content.get("clouds")
         if clouds_section is None:
@@ -166,12 +169,8 @@ class CloudsFileKeystoneCredentialsFixture(
                           "variable: %r", cloud_name)
                 self.cloud_name = cloud_name
             else:
-                message = "Undefined environment variable: 'OS_CLOUD'"
-                raise ValueError(message)
-        if not cloud_name:
-            message = "Invalid cloud name: {!r}".format(cloud_name)
-            raise ValueError(message)
-        return cloud_name
+                LOG.debug("Undefined environment variable: 'OS_CLOUD'")
+        return cloud_name or None
 
     def _get_clouds_content(self):
         clouds_content = self.clouds_content

tobiko/tests/unit/openstack/keystone/test_clouds_file.py

@@ -216,10 +216,11 @@ class CloudsFileKeystoneCredentialsFixtureTest(openstack.OpenstackTest):
             clouds_file=file_fixture.clouds_file,
             cloud_name='')
 
+        self.assertIsNone(credentials_fixture.credentials)
+        self.assertEqual('', credentials_fixture.cloud_name)
+        tobiko.setup_fixture(credentials_fixture)
+        self.assertIsNone(credentials_fixture.credentials)
         self.assertEqual('', credentials_fixture.cloud_name)
-        ex = self.assertRaises(ValueError, tobiko.setup_fixture,
-                               credentials_fixture)
-        self.assertEqual("Invalid cloud name: ''", str(ex))
 
     def test_setup_with_empty_cloud_name_from_env(self):
         file_fixture = self.useFixture(V2CloudsFileFixture())
@@ -227,20 +228,22 @@ class CloudsFileKeystoneCredentialsFixtureTest(openstack.OpenstackTest):
         credentials_fixture = keystone.CloudsFileKeystoneCredentialsFixture(
             clouds_file=file_fixture.clouds_file)
 
+        self.assertIsNone(credentials_fixture.credentials)
+        self.assertIsNone(credentials_fixture.cloud_name)
+        tobiko.setup_fixture(credentials_fixture)
+        self.assertIsNone(credentials_fixture.credentials)
         self.assertIsNone(credentials_fixture.cloud_name)
-        ex = self.assertRaises(ValueError, tobiko.setup_fixture,
-                               credentials_fixture)
-        self.assertEqual("Undefined environment variable: 'OS_CLOUD'", str(ex))
 
     def test_setup_with_no_cloud_name(self):
         file_fixture = self.useFixture(V2CloudsFileFixture())
         credentials_fixture = keystone.CloudsFileKeystoneCredentialsFixture(
             clouds_file=file_fixture.clouds_file)
 
+        self.assertIsNone(credentials_fixture.credentials)
+        self.assertIsNone(credentials_fixture.cloud_name)
+        tobiko.setup_fixture(credentials_fixture)
+        self.assertIsNone(credentials_fixture.credentials)
         self.assertIsNone(credentials_fixture.cloud_name)
-        ex = self.assertRaises(ValueError, tobiko.setup_fixture,
-                               credentials_fixture)
-        self.assertEqual("Undefined environment variable: 'OS_CLOUD'", str(ex))
 
     def test_setup_with_no_clouds_section(self):
         fixture = keystone.CloudsFileKeystoneCredentialsFixture(