Add extra failure codes to bad request exception

For instance on call to cloud.node_set_provision_state(uuid, 'dummy')
the API currently only returns:
(400) Client Error for url: http://127.0.0.1:6385/v1/nodes/<UUID>\
/states/provision Bad Request
whereas the HTTP request also contains some more valuable information
in the body:
The requested action "dummy" can not be performed on node "<UUID>" \
while it is in state "enroll".

Change-Id: I8412a2fd4ba78ad4f43ac2f13b1404dd3c151ce5

shade/exc.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 import sys
+import json
 
 import munch
 from requests import exceptions as _rex
@@ -140,6 +141,13 @@ def raise_from_response(response, error_message=None):
     except AttributeError:
         if response.reason:
             remote_error += " {reason}".format(reason=response.reason)
+        try:
+            json_resp = json.loads(details[detail_key])
+            fault_string = json_resp.get('faultstring')
+            if fault_string:
+                remote_error += " {fault}".format(fault=fault_string)
+        except Exception:
+            pass
 
     _log_response_extras(response)
 

shade/tests/unit/test_baremetal_node.py

@@ -858,6 +858,46 @@ class TestBaremetalNode(base.IronicTestCase):
         self.assertEqual(available_node, return_value)
         self.assert_calls()
 
+    def test_node_set_provision_state_bad_request(self):
+        self.fake_baremetal_node['provision_state'] = 'enroll'
+        self.register_uris([
+            dict(
+                method='PUT',
+                status_code=400,
+                json={'error': "{\"faultstring\": \"invalid state\"}"},
+                uri=self.get_mock_url(
+                    resource='nodes',
+                    append=[self.fake_baremetal_node['uuid'],
+                            'states', 'provision'])),
+        ])
+        self.assertRaisesRegexp(
+            exc.OpenStackCloudException,
+            '^Baremetal .* to dummy.*/states/provision invalid state$',
+            self.op_cloud.node_set_provision_state,
+            self.fake_baremetal_node['uuid'],
+            'dummy')
+        self.assert_calls()
+
+    def test_node_set_provision_state_bad_request_bad_json(self):
+        self.fake_baremetal_node['provision_state'] = 'enroll'
+        self.register_uris([
+            dict(
+                method='PUT',
+                status_code=400,
+                json={'error': 'invalid json'},
+                uri=self.get_mock_url(
+                    resource='nodes',
+                    append=[self.fake_baremetal_node['uuid'],
+                            'states', 'provision'])),
+        ])
+        self.assertRaisesRegexp(
+            exc.OpenStackCloudException,
+            '^Baremetal .* to dummy.*/states/provision$',
+            self.op_cloud.node_set_provision_state,
+            self.fake_baremetal_node['uuid'],
+            'dummy')
+        self.assert_calls()
+
     def test_wait_for_baremetal_node_lock_locked(self):
         self.fake_baremetal_node['reservation'] = 'conductor0'
         unlocked_node = self.fake_baremetal_node.copy()