Add gsutil 4.13 to telemetry/third_party

tools/telemetry/third_party/gsutil/third_party/gcs-oauth2-boto-plugin/README.md

Index: tools/telemetry/third_party/gsutil/third_party/gcs-oauth2-boto-plugin/README.md
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+# gcs-oauth2-boto-plugin
+
+gcs-oauth2-boto-plugin is a Python application whose purpose is to behave as
+an auth plugin for the [boto] auth plugin framework for use with [OAuth 2.0]
+credentials for the Google Cloud Platform. This plugin is compatible with
+both [user accounts] and [service accounts], and its functionality is
+essentially a wrapper around the oauth2client package of
+[google-api-python-client] with the addition of automatically caching tokens
+for the machine in a thread- and process-safe fashion.
+
+For more information about how to use this plugin to access Google Cloud Storage
+via boto in your application, see the [GCS documentation].
+
+If you wish to use this plugin without using the PyPI install as instructed in
+the documentation (e.g., for development), then you will need to manually
+acquire the modules from the requirements.txt file.
+
+
+When using this plugin, you must specify a client ID and secret. We offer the
+following methods for providing this information; if multiple methods are used,
+we will choose them in the following order:
+
+1. .boto config, if not set
+2. environment variables (OAUTH2_CLIENT_ID and OAUTH2_CLIENT_SECRET), if not set
+3. CLIENT_ID and CLIENT_SECRET values set by SetFallbackClientIdAndSecret function.
+
+Service accounts are supported via key files in either JSON or .p12 format.
+The file is first interpreted as JSON, with .p12 format as a fallback.
+
+The default locking mechanism used is threading.Lock. You can switch to using
+another locking mechanism by calling SetLock. Example:
+
+```
+SetLock(multiprocessing.Manager().Lock())
+```
+
+
+Before submitting any code, please run the tests (e.g., by running the following
+command from the root of this repository):
+
+    PYTHONPATH="." python -m gcs_oauth2_boto_plugin.test_oauth2_client
+
+[boto]: https://github.com/boto/boto
+[OAuth 2.0]: https://developers.google.com/accounts/docs/OAuth2Login
+[user accounts]: https://developers.google.com/accounts/docs/OAuth2#installed
+[service accounts]: https://developers.google.com/accounts/docs/OAuth2#serviceaccount
+[google-api-python-client]: https://code.google.com/p/google-api-python-client/wiki/OAuth2Client
+[GCS documentation]: https://developers.google.com/storage/docs/gspythonlibrary