Use assertRaises for asserting if subject threw an exception

Closes #674
This change ensures that, should a regression happen, the test
will print a more helpful failure message than "True is not False"

libcloud/test/compute/test_dimensiondata.py

@@ -43,19 +43,14 @@ def setUp(self):
         self.driver = DimensionData(*DIMENSIONDATA_PARAMS)
 
     def test_invalid_region(self):
-        try:
-            self.driver = DimensionData(*DIMENSIONDATA_PARAMS, region='blah')
-        except ValueError:
-            pass
+        self.assertRaises(ValueError,
+                          DimensionData,
+                          *DIMENSIONDATA_PARAMS,
+                          region='blah')
 
     def test_invalid_creds(self):
         DimensionDataMockHttp.type = 'UNAUTHORIZED'
-        try:
-            self.driver.list_nodes()
-            self.assertTrue(
-                False)  # Above command should have thrown an InvalidCredsException
-        except InvalidCredsError:
-            pass
+        self.assertRaises(InvalidCredsError, self.driver.list_nodes)
 
     def test_list_locations_response(self):
         DimensionDataMockHttp.type = None
@@ -88,12 +83,7 @@ def test_reboot_node_response_INPROGRESS(self):
         DimensionDataMockHttp.type = 'INPROGRESS'
         node = Node(id='11', name=None, state=None,
                     public_ips=None, private_ips=None, driver=self.driver)
-        try:
-            node.reboot()
-            self.assertTrue(
-                False)  # above command should have thrown DimensionDataAPIException
-        except DimensionDataAPIException:
-            pass
+        self.assertRaises(DimensionDataAPIException, node.reboot)
 
     def test_destroy_node_response(self):
         node = Node(id='11', name=None, state=None,
@@ -105,12 +95,7 @@ def test_destroy_node_response_RESOURCE_BUSY(self):
         DimensionDataMockHttp.type = 'INPROGRESS'
         node = Node(id='11', name=None, state=None,
                     public_ips=None, private_ips=None, driver=self.driver)
-        try:
-            node.destroy()
-            self.assertTrue(
-                False)  # above command should have thrown DimensionDataAPIException
-        except DimensionDataAPIException:
-            pass
+        self.assertRaises(DimensionDataAPIException, node.destroy)
 
     def test_list_images(self):
         images = self.driver.list_images()
@@ -163,12 +148,15 @@ def test_create_node_response_network_domain(self):
     def test_create_node_no_network(self):
         rootPw = NodeAuthPassword('pass123')
         image = self.driver.list_images()[0]
-        try:
-            self.driver.create_node(name='test2', image=image, auth=rootPw,
-                                    ex_description='test2 node', ex_network=None,
-                                    ex_isStarted=False)
-        except ValueError:
-            pass
+        self.assertRaises(
+            ValueError,
+            self.driver.create_node,
+            name='test2',
+            image=image,
+            auth=rootPw,
+            ex_description='test2 node',
+            ex_network=None,
+            ex_isStarted=False)
 
     def test_ex_shutdown_graceful(self):
         node = Node(id='11', name=None, state=None,
@@ -180,12 +168,9 @@ def test_ex_shutdown_graceful_INPROGRESS(self):
         DimensionDataMockHttp.type = 'INPROGRESS'
         node = Node(id='11', name=None, state=None,
                     public_ips=None, private_ips=None, driver=self.driver)
-        try:
-            self.driver.ex_shutdown_graceful(node)
-            self.assertTrue(
-                False)  # above command should have thrown DimensionDataAPIException
-        except DimensionDataAPIException:
-            pass
+        self.assertRaises(DimensionDataAPIException,
+                          self.driver.ex_shutdown_graceful,
+                          node)
 
     def test_ex_start_node(self):
         node = Node(id='11', name=None, state=None,
@@ -197,12 +182,9 @@ def test_ex_start_node_INPROGRESS(self):
         DimensionDataMockHttp.type = 'INPROGRESS'
         node = Node(id='11', name=None, state=None,
                     public_ips=None, private_ips=None, driver=self.driver)
-        try:
-            self.driver.ex_start_node(node)
-            self.assertTrue(
-                False)  # above command should have thrown DimensionDataAPIException
-        except DimensionDataAPIException:
-            pass
+        self.assertRaises(DimensionDataAPIException,
+                          self.driver.ex_start_node,
+                          node)
 
     def test_ex_power_off(self):
         node = Node(id='11', name=None, state=None,
@@ -220,12 +202,9 @@ def test_ex_power_off_INPROGRESS(self):
         DimensionDataMockHttp.type = 'INPROGRESS'
         node = Node(id='11', name=None, state=None,
                     public_ips=None, private_ips=None, driver=self.driver)
-        try:
-            self.driver.ex_power_off(node)
-            self.assertTrue(
-                False)  # above command should have thrown DimensionDataAPIException
-        except DimensionDataAPIException:
-            pass
+        self.assertRaises(DimensionDataAPIException,
+                          self.driver.ex_power_off,
+                          node)
 
     def test_ex_reset(self):
         node = Node(id='11', name=None, state=None,
@@ -237,7 +216,7 @@ def test_ex_attach_node_to_vlan(self):
         node = self.driver.ex_get_node_by_id('e75ead52-692f-4314-8725-c8a4f4d13a87')
         vlan = self.driver.ex_get_vlan('0e56433f-d808-4669-821d-812769517ff8')
         ret = self.driver.ex_attach_node_to_vlan(node, vlan)
-        self.assertTrue(ret)
+        self.assertTrue(ret is True)
 
     def test_ex_destroy_nic(self):
         node = self.driver.ex_destroy_nic('a202e51b-41c0-4cfc-add0-b1c62fc0ecf6')