Roll cq_client.

third_party/cq_client/README.md

+# CQ Client Library.
+
 This directory contains CQ client library to be distributed to other repos. If
 you need to modify some files in this directory, please make sure that you are
 changing the canonical version of the source code and not one of the copies,
 which should only be updated as a whole using Glyco (when available, see
 [chromium issue 489420](http://crbug.com/489420)).
 
-The canonical version is located at `https://chrome-internal.googlesource.com/
-infra/infra_internal/+/master/commit_queue/cq_client`.
+The canonical version is located at
+[https://chrome-internal.googlesource.com/infra/infra_internal/+/master/commit_queue/cq_client]().
 
-You'll need to use protoc version 2.6.1 and
-recent golang/protobuf package. Sadly, the latter has neither tags nor versions.
+When modifying cq.proto, consider adding checks to validator in
+[https://chrome-internal.googlesource.com/infra/infra_internal/+/master/appengine/commit_queue/src/commitqueue/validate.go]().
 
-You can get protobuf by downloading archive from
-https://github.com/google/protobuf/tree/v2.6.1 and manually building it. As for
-golang compiler, if you have go configured, just
 
-    go get -u github.com/golang/protobuf/{proto,protoc-gen-go}
+## Generation of Python and Go bindings
 
-TODO(tandrii,sergiyb): decide how to pin the go protobuf generator.
+### tl;dr
+  
+    make
 
-To generate `cq_pb2.py` and `cq.pb.go`:
 
-    cd commit_queue/cq_client
-    protoc cq.proto --python_out $(pwd) --go_out $(pwd)
+### Details
 
-Additionally, please make sure to use proto3-compatible syntax, e.g. no default
-values, no required fields. Ideally, we should use proto3 generator already,
-however alpha version thereof is still unstable.
+All commands below assume you are working in a standard infra_internal gclient
+checkout (e.g., after you ran `mkdir src && cd src && fetch infra_internal`) and
+are in current directory of this README.md (that is, in
+`cd infra_internal/commit_queue/cq_client`).
 
+To generate Python's `cq_pb2.py` you'll need to get and `protoc` of version
+**2.6.1**. You can get it by `make py-prepare`.
+    
+    make py
+
+To generate Golang's protobuf file `cq.pb.go`, you'll need to bootstrap
+infra/infra repository and go utilities `make go-prepare`.
+
+    make go
+
+## Notes
+
+1. Please make sure to use proto3-compatible yntax, e.g. no default
+values, no required fields. As of this writing (Jan 2016),
+the Go protobuf compiler has been upgraded to 3.0.0. So, if you can generate go
+bindings, all is good.
+
+2. If after generating Python binding, CQ tests fail with:
+
+        TypeError: __init__() got an unexpected keyword argument 'syntax'
+
+You've probably used 3.0.0 protoc generator. We should eventually switch to 3x
+Python version as well, but it requires upgrading infra's Python ENV to newer
+package. See [bootstrap/README.md](../../bootstrap/README.md) for more
+information.  We may end up deprecating Python before all infra's Python code
+can be moved to protobuf v3.