diff --git a/src/python/grpcio/grpc/_cython/_cygrpc/aio/call.pyx.pxi b/src/python/grpcio/grpc/_cython/_cygrpc/aio/call.pyx.pxi
index 5129e2efed4..b64f952fca5 100644
--- a/src/python/grpcio/grpc/_cython/_cygrpc/aio/call.pyx.pxi
+++ b/src/python/grpcio/grpc/_cython/_cygrpc/aio/call.pyx.pxi
@@ -125,7 +125,7 @@ cdef class _AioCall(GrpcCallWrapper):
         if credentials is not None:
             set_credentials_error = grpc_call_set_credentials(self.call, credentials.c())
             if set_credentials_error != GRPC_CALL_OK:
-                raise RuntimeError("Credentials couldn't have been set")
+                raise RuntimeError(f"Credentials couldn't have been set: {set_credentials_error}")
 
         grpc_slice_unref(method_slice)
 
@@ -209,7 +209,7 @@ cdef class _AioCall(GrpcCallWrapper):
 
     def done(self):
         """Returns if the RPC call has finished.
-        
+
         Checks if the status has been provided, either
         because the RPC finished or because was cancelled..
 
@@ -220,7 +220,7 @@ cdef class _AioCall(GrpcCallWrapper):
 
     def cancelled(self):
         """Returns if the RPC was cancelled.
-        
+
         Returns:
             True if the RPC was cancelled.
         """
@@ -231,7 +231,7 @@ cdef class _AioCall(GrpcCallWrapper):
 
     async def status(self):
         """Returns the status of the RPC call.
-        
+
         It returns the finshed status of the RPC. If the RPC
         has not finished yet this function will wait until the RPC
         gets finished.
@@ -254,7 +254,7 @@ cdef class _AioCall(GrpcCallWrapper):
 
     async def initial_metadata(self):
         """Returns the initial metadata of the RPC call.
-        
+
         If the initial metadata has not been received yet this function will
         wait until the RPC gets finished.
 
@@ -420,7 +420,7 @@ cdef class _AioCall(GrpcCallWrapper):
                            tuple outbound_initial_metadata,
                            object metadata_sent_observer):
         """Actual implementation of the complete unary-stream call.
-        
+
         Needs to pay extra attention to the raise mechanism. If we want to
         propagate the final status exception, then we have to raise it.
         Othersize, it would end normally and raise `StopAsyncIteration()`.
@@ -490,7 +490,7 @@ cdef class _AioCall(GrpcCallWrapper):
                                         outbound_initial_metadata,
                                         self._send_initial_metadata_flags,
                                         self._loop)
-            # Notify upper level that sending messages are allowed now.   
+            # Notify upper level that sending messages are allowed now.
             metadata_sent_observer()
 
             # Receives initial metadata.
diff --git a/src/python/grpcio_tests/tests_aio/unit/_test_server.py b/src/python/grpcio_tests/tests_aio/unit/_test_server.py
index bcc6e3bc304..e5ec53f1476 100644
--- a/src/python/grpcio_tests/tests_aio/unit/_test_server.py
+++ b/src/python/grpcio_tests/tests_aio/unit/_test_server.py
@@ -24,6 +24,10 @@ from tests_aio.unit import _constants
 
 _INITIAL_METADATA_KEY = "x-grpc-test-echo-initial"
 _TRAILING_METADATA_KEY = "x-grpc-test-echo-trailing-bin"
+_PRIVATE_KEY = resources.private_key()
+_CERTIFICATE_CHAIN = resources.certificate_chain()
+_TEST_ROOT_CERTIFICATES = resources.test_root_certificates()
+_SERVER_CERTS = ((_PRIVATE_KEY, _CERTIFICATE_CHAIN),)
 
 
 async def _maybe_echo_metadata(servicer_context):
@@ -38,11 +42,6 @@ async def _maybe_echo_metadata(servicer_context):
                               invocation_metadata[_TRAILING_METADATA_KEY])
         servicer_context.set_trailing_metadata((trailing_metadatum,))
 
-_PRIVATE_KEY = resources.private_key()
-_CERTIFICATE_CHAIN = resources.certificate_chain()
-_TEST_ROOT_CERTIFICATES = resources.test_root_certificates()
-_SERVER_CERTS = ((_PRIVATE_KEY, _CERTIFICATE_CHAIN),)
-
 
 async def _maybe_echo_status(request: messages_pb2.SimpleRequest,
                              servicer_context):