raise AttributeError for azure.core.pipeline.transport.__bases__ (Azure#22470)

* raise AttributeError for azure.core.pipeline.transport.__bases__

* update changelog

Author: xiangyan99

sdk/core/azure-core/CHANGELOG.md

@@ -8,6 +8,8 @@
 
 ### Bugs Fixed
 
+- raise AttributeError when calling azure.core.pipeline.transport.\_\_bases__    #22469
+
 ### Other Changes
 
 ## 1.21.1 (2021-12-06)

sdk/core/azure-core/azure/core/pipeline/transport/__init__.py

@@ -87,6 +87,8 @@ def __getattr__(name):
                         return TrioRequestsTransportResponse
                     except ImportError:
                         raise ImportError("trio package is not installed")
+                if name == '__bases__':
+                    raise AttributeError("module 'azure.core.pipeline.transport' has no attribute '__bases__'")
                 return name
 
         else: