Raise on bad credential (Azure#16206)

Author: Rakshith Bhyravabhotla

sdk/eventgrid/azure-eventgrid/CHANGELOG.md

@@ -7,6 +7,7 @@
 
   **Bug Fixes**
   - `EventGridEvent` has two additional required positional parameters namely, `data` and `data_version`.
+  - `EventGridPublisherClient` now appropriately throws a `ValueError` if an invalid credential is passed during initialization.
 
 ## 2.0.0b4 (2020-11-11)
 

sdk/eventgrid/azure-eventgrid/azure/eventgrid/_helpers.py

@@ -77,13 +77,13 @@ def _get_authentication_policy(credential):
     if credential is None:
         raise ValueError("Parameter 'self._credential' must not be None.")
     if isinstance(credential, AzureKeyCredential):
-        authentication_policy = AzureKeyCredentialPolicy(credential=credential, name=constants.EVENTGRID_KEY_HEADER)
+        return AzureKeyCredentialPolicy(credential=credential, name=constants.EVENTGRID_KEY_HEADER)
     if isinstance(credential, AzureSasCredential):
-        authentication_policy = EventGridSasCredentialPolicy(
+        return EventGridSasCredentialPolicy(
             credential=credential,
             name=constants.EVENTGRID_TOKEN_HEADER
         )
-    return authentication_policy
+    raise ValueError("The provided credential should be an instance of AzureSasCredential or AzureKeyCredential")
 
 def _is_cloud_event(event):
     # type: (Any) -> bool

sdk/eventgrid/azure-eventgrid/tests/test_eg_publisher_client.py

@@ -238,3 +238,8 @@ def test_send_custom_schema_event_as_list(self, resource_group, eventgrid_topic,
                     }
                 )
         client.send([custom_event1, custom_event2])
+
+    def test_send_throws_with_bad_credential(self):
+        bad_credential = "I am a bad credential"
+        with pytest.raises(ValueError, match="The provided credential should be an instance of AzureSasCredential or AzureKeyCredential"):
+            client = EventGridPublisherClient("eventgrid_endpoint", bad_credential)