vendor update for CSI 0.3.0

vendor/google.golang.org/grpc/Documentation/rpc-errors.md

@@ -0,0 +1,68 @@
+# RPC Errors
+
+All service method handlers should return `nil` or errors from the
+`status.Status` type. Clients have direct access to the errors.
+
+Upon encountering an error, a gRPC server method handler should create a
+`status.Status`. In typical usage, one would use [status.New][new-status]
+passing in an appropriate [codes.Code][code] as well as a description of the
+error to produce a `status.Status`. Calling [status.Err][status-err] converts
+the `status.Status` type into an `error`. As a convenience method, there is also
+[status.Error][status-error] which obviates the conversion step. Compare:
+
+```
+st := status.New(codes.NotFound, "some description")
+err := st.Err()
+
+// vs.
+
+err := status.Error(codes.NotFound, "some description")
+```
+
+## Adding additional details to errors
+
+In some cases, it may be necessary to add details for a particular error on the
+server side. The [status.WithDetails][with-details] method exists for this
+purpose. Clients may then read those details by first converting the plain
+`error` type back to a [status.Status][status] and then using
+[status.Details][details].
+
+## Example
+
+The [example][example] demonstrates the API discussed above and shows how to add
+information about rate limits to the error message using `status.Status`.
+
+To run the example, first start the server:
+
+```
+$ go run examples/rpc_errors/server/main.go
+```
+
+In a separate session, run the client:
+
+```
+$ go run examples/rpc_errors/client/main.go
+```
+
+On the first run of the client, all is well:
+
+```
+2018/03/12 19:39:33 Greeting: Hello world
+```
+
+Upon running the client a second time, the client exceeds the rate limit and
+receives an error with details:
+
+```
+2018/03/19 16:42:01 Quota failure: violations:<subject:"name:world" description:"Limit one greeting per person" >
+exit status 1
+```
+
+[status]:       https://godoc.org/google.golang.org/grpc/status#Status
+[new-status]:   https://godoc.org/google.golang.org/grpc/status#New
+[code]:         https://godoc.org/google.golang.org/grpc/codes#Code
+[with-details]: https://godoc.org/google.golang.org/grpc/status#Status.WithDetails
+[details]:      https://godoc.org/google.golang.org/grpc/status#Status.Details
+[status-err]:   https://godoc.org/google.golang.org/grpc/status#Status.Err
+[status-error]: https://godoc.org/google.golang.org/grpc/status#Error
+[example]:      https://github.com/grpc/grpc-go/blob/master/examples/rpc_errors