fix: use api-core exception

Author: busunkim96

gapic/templates/%namespace/%name_%version/%sub/services/%service/client.py.j2

@@ -210,7 +210,7 @@ class {{ service.client_name }}(metaclass={{ service.client_name }}Meta):
             self._transport = Transport(
                 credentials=credentials,
                 credentials_file=client_options.credentials_file,
-                host=self.DEFAULT_ENDPOINT,
+                host=client_options.api_endpoint,
                 scopes=client_options.scopes,
                 api_mtls_endpoint=client_options.api_endpoint,
                 client_cert_source=client_options.client_cert_source,

gapic/templates/%namespace/%name_%version/%sub/services/%service/transports/base.py.j2

@@ -5,6 +5,7 @@ import abc
 import typing
 
 from google import auth
+from google.api_core import exceptions  # type: ignore
 {%- if service.has_lro %}
 from google.api_core import operations_v1  # type: ignore
 {%- endif %}
@@ -57,7 +58,7 @@ class {{ service.name }}Transport(abc.ABC):
         # If no credentials are provided, then determine the appropriate
         # defaults.
         if credentials and credentials_file:
-            raise ValueError("'credentials_file' and 'credentials' are mutually exclusive")
+            raise exceptions.DuplicateCredentialArgs("'credentials_file' and 'credentials' are mutually exclusive")
 
         if credentials_file is not None:
             credentials, _ = auth.load_credentials_from_file(credentials_file, scopes=scopes)

gapic/templates/%namespace/%name_%version/%sub/services/%service/transports/grpc.py.j2

@@ -75,7 +75,8 @@ class {{ service.name }}GrpcTransport({{ service.name }}Transport):
         Raises:
           google.auth.exceptions.MutualTLSChannelError: If mutual TLS transport
               creation failed for any reason.
-          ValueError: If both ``credentials`` and ``credentials_file`` are passed.
+          google.api_core.exceptions.DuplicateCredentialArgs: If both ``credentials``
+              and ``credentials_file`` are passed.
         """
         if channel:
             # Sanity check: Ensure that channel and credentials are not both
@@ -110,7 +111,13 @@ class {{ service.name }}GrpcTransport({{ service.name }}Transport):
             )
 
         # Run the base constructor.
-        super().__init__(host=host, credentials=credentials, credentials_file=credentials_file, scopes=scopes)
+        super().__init__(
+            host=host,
+            credentials=credentials,
+            credentials_file=credentials_file,
+            scopes=scopes or self.AUTH_SCOPES
+        )
+
         self._stubs = {}  # type: Dict[str, Callable]
 
     @classmethod
@@ -140,7 +147,8 @@ class {{ service.name }}GrpcTransport({{ service.name }}Transport):
             grpc.Channel: A gRPC channel object.
 
         Raises:
-            ValueError: If both ``credentials`` and ``credentials_file`` are passed.
+            google.api_core.exceptions.DuplicateCredentialArgs: If both ``credentials``
+              and ``credentials_file`` are passed.
         """
         scopes = scopes or cls.AUTH_SCOPES
         return grpc_helpers.create_channel(

gapic/templates/%namespace/%name_%version/%sub/services/%service/transports/grpc_asyncio.py.j2

@@ -43,6 +43,7 @@ class {{ service.grpc_asyncio_transport_name }}({{ service.name }}Transport):
     def create_channel(cls,
                        host: str{% if service.host %} = '{{ service.host }}'{% endif %},
                        credentials: credentials.Credentials = None,
+                       credentials_file: Optional[str] = None,
                        scopes: Optional[Sequence[str]] = None,
                        **kwargs) -> aio.Channel:
         """Create and return a gRPC AsyncIO channel object.
@@ -53,6 +54,9 @@ class {{ service.grpc_asyncio_transport_name }}({{ service.name }}Transport):
                 credentials identify this application to the service. If
                 none are specified, the client will attempt to ascertain
                 the credentials from the environment.
+            credentials_file (Optional[str]): A file with credentials that can
+                be loaded with :func:`google.auth.load_credentials_from_file`.
+                This argument is ignored if ``channel`` is provided.
             scopes (Optional[Sequence[str]]): A optional list of scopes needed for this
                 service. These are only used when credentials are not specified and
                 are passed to :func:`google.auth.default`.
@@ -65,13 +69,16 @@ class {{ service.grpc_asyncio_transport_name }}({{ service.name }}Transport):
         return grpc_helpers_async.create_channel(
             host,
             credentials=credentials,
+            credentials_file=credentials_file,
             scopes=scopes,
             **kwargs
         )
 
     def __init__(self, *,
             host: str{% if service.host %} = '{{ service.host }}'{% endif %},
             credentials: credentials.Credentials = None,
+            credentials_file: Optional[str] = None,
+            scopes: Optional[Sequence[str]] = None,
             channel: aio.Channel = None,
             api_mtls_endpoint: str = None,
             client_cert_source: Callable[[], Tuple[bytes, bytes]] = None) -> None:
@@ -86,6 +93,12 @@ class {{ service.grpc_asyncio_transport_name }}({{ service.name }}Transport):
                 are specified, the client will attempt to ascertain the
                 credentials from the environment.
                 This argument is ignored if ``channel`` is provided.
+            credentials_file (Optional[str]): A file with credentials that can
+                be loaded with :func:`google.auth.load_credentials_from_file`.
+                This argument is ignored if ``channel`` is provided.
+            scopes (Optional[Sequence[str]]): A optional list of scopes needed for this
+                service. These are only used when credentials are not specified and
+                are passed to :func:`google.auth.default`.
             channel (Optional[aio.Channel]): A ``Channel`` instance through
                 which to make calls.
             api_mtls_endpoint (Optional[str]): The mutual TLS endpoint. If
@@ -98,8 +111,10 @@ class {{ service.grpc_asyncio_transport_name }}({{ service.name }}Transport):
                 is None.
 
         Raises:
-          google.auth.exceptions.MutualTlsChannelError: If mutual TLS transport
+            google.auth.exceptions.MutualTlsChannelError: If mutual TLS transport
               creation failed for any reason.
+          google.api_core.exceptions.DuplicateCredentialArgs: If both ``credentials``
+              and ``credentials_file`` are passed.
         """
         if channel:
             # Sanity check: Ensure that channel and credentials are not both
@@ -125,12 +140,19 @@ class {{ service.grpc_asyncio_transport_name }}({{ service.name }}Transport):
             self._grpc_channel = type(self).create_channel(
                 host,
                 credentials=credentials,
+                credentials_file=credentials_file,
                 ssl_credentials=ssl_credentials,
-                scopes=self.AUTH_SCOPES,
+                scopes=scopes or self.AUTH_SCOPES,
             )
 
         # Run the base constructor.
-        super().__init__(host=host, credentials=credentials)
+        super().__init__(
+            host=host,
+            credentials=credentials,
+            credentials_file=credentials_file,
+            scopes=scopes or self.AUTH_SCOPES
+        )
+
         self._stubs = {}
 
     @property