Handle errors in GETs gracefully

If a call to send_api_request hits an exception,
it will return None. However, our code that expects iterable
types are returned from many of our GETs. This change replaces
None returns with empty dicts in such cases.

Change-Id: I6be1ee4f84fd38519d7c5ae227581a1a72964fa0

networking_arista/ml2/rpc/arista_json.py

@@ -103,6 +103,7 @@ class AristaRPCWrapperJSON(AristaRPCWrapperBase):
             # reraise the exception
             with excutils.save_and_reraise_exception() as ctxt:
                 ctxt.reraise = True
+        return {} if method == 'GET' else None
 
     def _check_if_cvx_leader(self, host):
         url = 'agent/'

networking_arista/tests/unit/ml2/rpc/test_arista_json_rpc_wrapper.py

@@ -15,6 +15,7 @@
 
 import functools
 import operator
+import requests
 import socket
 
 import mock
@@ -656,6 +657,32 @@ class TestAristaJSONRPCWrapper(testlib_api.SqlTestCase):
         ]
         self._verify_send_api_request_call(mock_send_api_req, calls)
 
+    @patch('requests.get')
+    @patch(BASE_RPC + '_get_eos_master')
+    def test_get_value_error(self, mock_get_eos_master, mock_requests_get):
+        mock_get_eos_master.return_value = 'fake_master'
+        mock_requests_get.return_value = requests.Response()
+        self.assertIsNotNone(self.drv.get_vms_for_tenant(''))
+        self.assertIsNotNone(self.drv.get_dhcps_for_tenant(''))
+        self.assertIsNotNone(self.drv.get_baremetals_for_tenant(''))
+        self.assertIsNotNone(self.drv.get_routers_for_tenant(''))
+        self.assertIsNotNone(self.drv.get_ports_for_tenant('', 'vm'))
+        self.assertIsNotNone(self.drv.get_tenants())
+        self.assertIsNotNone(self.drv.get_networks(''))
+        self.assertIsNotNone(self.drv.get_instance_ports('', 'vm'))
+
+    @patch(BASE_RPC + '_get_eos_master')
+    def test_get_exception(self, mock_get_eos_master):
+        mock_get_eos_master.return_value = 'fake_master'
+        self.assertIsNotNone(self.drv.get_vms_for_tenant(''))
+        self.assertIsNotNone(self.drv.get_dhcps_for_tenant(''))
+        self.assertIsNotNone(self.drv.get_baremetals_for_tenant(''))
+        self.assertIsNotNone(self.drv.get_routers_for_tenant(''))
+        self.assertIsNotNone(self.drv.get_ports_for_tenant('', 'vm'))
+        self.assertIsNotNone(self.drv.get_tenants())
+        self.assertIsNotNone(self.drv.get_networks(''))
+        self.assertIsNotNone(self.drv.get_instance_ports('', 'vm'))
+
 
 class RPCWrapperJSONValidConfigTrunkTestCase(testlib_api.SqlTestCase):
     """Test cases to test plug trunk port into network. """