add back elif policy

sdk/core/corehttp/corehttp/runtime/pipeline/_base.py

@@ -140,6 +140,10 @@ def __init__(
                 self._impl_policies.append(policy)
             elif is_sansio_http_policy(policy):
                 self._impl_policies.append(_SansIOHTTPPolicyRunner(policy))
+            elif policy:
+                raise AttributeError(
+                    f"'{type(policy)}' object has no attribute 'send' or 'on_request' and 'on_response'."
+                )
         for index in range(len(self._impl_policies) - 1):
             self._impl_policies[index].next = self._impl_policies[index + 1]
         if self._impl_policies:

sdk/core/corehttp/corehttp/runtime/pipeline/_base_async.py

@@ -138,6 +138,10 @@ def __init__(
                 self._impl_policies.append(policy)
             elif is_sansio_http_policy(policy):
                 self._impl_policies.append(_SansIOAsyncHTTPPolicyRunner(policy))
+            elif policy:
+                raise AttributeError(
+                    f"'{type(policy)}' object has no attribute 'send' or 'on_request' and 'on_response'."
+                )
         for index in range(len(self._impl_policies) - 1):
             self._impl_policies[index].next = self._impl_policies[index + 1]
         if self._impl_policies:

sdk/core/corehttp/tests/async_tests/test_pipeline_async.py

@@ -49,6 +49,14 @@ async def __aexit__(self, exc_type, exc_value, traceback):
         await pipeline.run(req)
 
 
+def test_invalid_policy_error():
+    class FooPolicy:
+        pass
+
+    with pytest.raises(AttributeError):
+        pipeline = Pipeline(transport=Mock(), policies=[FooPolicy()])
+
+
 @pytest.mark.asyncio
 @pytest.mark.parametrize("transport", ASYNC_TRANSPORTS)
 async def test_transport_socket_timeout(transport):

sdk/core/corehttp/tests/test_pipeline.py

@@ -4,6 +4,7 @@
 # license information.
 # -------------------------------------------------------------------------
 
+from unittest.mock import Mock
 import json
 from io import BytesIO
 import xml.etree.ElementTree as ET
@@ -52,6 +53,14 @@ def __exit__(self, exc_type, exc_value, traceback):
         pipeline.run(req)
 
 
+def test_invalid_policy_error():
+    class FooPolicy:
+        pass
+
+    with pytest.raises(AttributeError):
+        pipeline = Pipeline(transport=Mock(), policies=[FooPolicy()])
+
+
 @pytest.mark.parametrize("transport", SYNC_TRANSPORTS)
 def test_transport_socket_timeout(transport):
     request = HttpRequest("GET", "https://bing.com")