docs: remove references to the old authentication credentials (#9456)

Author: emar-kar

api_core/docs/auth.rst

@@ -177,22 +177,6 @@ described above,
 so be sure none of the other possible environments conflict
 with your user provided credentials.
 
-Advanced users of `oauth2client`_ can also use custom flows to
-create credentials using `client secrets`_ or using a
-`webserver flow`_.
-After creation, :class:`Credentials <oauth2client.client.Credentials>`
-can be serialized with
-:meth:`to_json() <oauth2client.client.Credentials.to_json>`
-and stored in a file and then and deserialized with
-:meth:`from_json() <oauth2client.client.Credentials.from_json>`. In order
-to use ``oauth2client``'s credentials with this library, you'll need to
-`convert them`_.
-
-.. _oauth2client: https://github.com/Google/oauth2client
-.. _client secrets: https://developers.google.com/api-client-library/python/guide/aaa_oauth#flow_from_clientsecrets
-.. _webserver flow: https://developers.google.com/api-client-library/python/guide/aaa_oauth#OAuth2WebServerFlow
-.. _convert them: http://google-auth.readthedocs.io/en/stable/user-guide.html#user-credentials
-
 Troubleshooting
 ===============
 

error_reporting/google/cloud/error_reporting/_logging.py

@@ -30,12 +30,12 @@ class _ErrorReportingLoggingAPI(object):
                     passed falls back to the default inferred from the
                     environment.
 
-    :type credentials: :class:`oauth2client.client.OAuth2Credentials` or
+    :type credentials: :class:`google.auth.credentials.Credentials` or
                        :class:`NoneType`
-    :param credentials: The OAuth2 Credentials to use for the connection
-                        owned by this client. If not passed (and if no
-                        ``_http`` object is passed), falls back to the default
-                        inferred from the environment.
+    :param credentials: The authorization credentials to attach to requests.
+                        These credentials identify this application to the service.
+                        If none are specified, the client will attempt to ascertain
+                        the credentials from the environment.
 
     :type _http: :class:`~requests.Session`
     :param _http: (Optional) HTTP object to make requests. Can be any object

error_reporting/google/cloud/error_reporting/client.py

@@ -96,12 +96,12 @@ class Client(ClientWithProject):
                     passed falls back to the default inferred from the
                     environment.
 
-    :type credentials: :class:`oauth2client.client.OAuth2Credentials` or
+    :type credentials: :class:`google.auth.credentials.Credentials` or
                        :class:`NoneType`
-    :param credentials: The OAuth2 Credentials to use for the connection
-                        owned by this client. If not passed (and if no
-                        ``_http`` object is passed), falls back to the default
-                        inferred from the environment.
+    :param credentials: The authorization credentials to attach to requests.
+                        These credentials identify this application to the service.
+                        If none are specified, the client will attempt to ascertain
+                        the credentials from the environment.
 
     :type _http: :class:`~requests.Session`
     :param _http: (Optional) HTTP object to make requests. Can be any object

spanner/google/cloud/spanner_v1/client.py

@@ -93,11 +93,12 @@ class Client(ClientWithProject):
                     attempt to determine from the environment.
 
     :type credentials:
-        :class:`OAuth2Credentials <oauth2client.client.OAuth2Credentials>` or
+        :class:`Credentials <google.auth.credentials.Credentials>` or
         :data:`NoneType <types.NoneType>`
-    :param credentials: (Optional) The OAuth2 Credentials to use for this
-                        client. If not provided, defaults to the Google
-                        Application Default Credentials.
+    :param credentials: (Optional) The authorization credentials to attach to requests.
+                        These credentials identify this application to the service.
+                        If none are specified, the client will attempt to ascertain
+                        the credentials from the environment.
 
     :type client_info: :class:`google.api_core.gapic_v1.client_info.ClientInfo`
     :param client_info:
@@ -143,7 +144,7 @@ def credentials(self):
         """Getter for client's credentials.
 
         :rtype:
-            :class:`OAuth2Credentials <oauth2client.client.OAuth2Credentials>`
+            :class:`Credentials <google.auth.credentials.Credentials>`
         :returns: The credentials stored on the client.
         """
         return self._credentials

storage/google/cloud/storage/blob.py

@@ -430,11 +430,12 @@ def generate_signed_url(
                        to the ``client`` stored on the blob's bucket.
 
 
-        :type credentials: :class:`oauth2client.client.OAuth2Credentials` or
+        :type credentials: :class:`google.auth.credentials.Credentials` or
                            :class:`NoneType`
-        :param credentials: (Optional) The OAuth2 credentials to use to sign
-                            the URL. Defaults to the credentials stored on the
-                            client used.
+        :param credentials: The authorization credentials to attach to requests.
+                            These credentials identify this application to the service.
+                            If none are specified, the client will attempt to ascertain
+                            the credentials from the environment.
 
         :type version: str
         :param version: (Optional) The version of signed credential to create.

storage/google/cloud/storage/bucket.py

@@ -2121,11 +2121,12 @@ def generate_signed_url(
                        to the ``client`` stored on the blob's bucket.
 
 
-        :type credentials: :class:`oauth2client.client.OAuth2Credentials` or
+        :type credentials: :class:`google.auth.credentials.Credentials` or
                            :class:`NoneType`
-        :param credentials: (Optional) The OAuth2 credentials to use to sign
-                            the URL. Defaults to the credentials stored on the
-                            client used.
+        :param credentials: The authorization credentials to attach to requests.
+                            These credentials identify this application to the service.
+                            If none are specified, the client will attempt to ascertain
+                            the credentials from the environment.
 
         :type version: str
         :param version: (Optional) The version of signed credential to create.