diff --git a/buildstream/_protos/google/rpc/code.proto b/buildstream/_protos/google/rpc/code.proto
new file mode 100644
index 0000000000000000000000000000000000000000..74e2c5c9ada78c5d91ce28439eec50ed24417391
--- /dev/null
+++ b/buildstream/_protos/google/rpc/code.proto
@@ -0,0 +1,186 @@
+// Copyright 2017 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+syntax = "proto3";
+
+package google.rpc;
+
+option go_package = "google.golang.org/genproto/googleapis/rpc/code;code";
+option java_multiple_files = true;
+option java_outer_classname = "CodeProto";
+option java_package = "com.google.rpc";
+option objc_class_prefix = "RPC";
+
+
+// The canonical error codes for Google APIs.
+//
+//
+// Sometimes multiple error codes may apply. Services should return
+// the most specific error code that applies. For example, prefer
+// `OUT_OF_RANGE` over `FAILED_PRECONDITION` if both codes apply.
+// Similarly prefer `NOT_FOUND` or `ALREADY_EXISTS` over `FAILED_PRECONDITION`.
+enum Code {
+ // Not an error; returned on success
+ //
+ // HTTP Mapping: 200 OK
+ OK = 0;
+
+ // The operation was cancelled, typically by the caller.
+ //
+ // HTTP Mapping: 499 Client Closed Request
+ CANCELLED = 1;
+
+ // Unknown error. For example, this error may be returned when
+ // a `Status` value received from another address space belongs to
+ // an error space that is not known in this address space. Also
+ // errors raised by APIs that do not return enough error information
+ // may be converted to this error.
+ //
+ // HTTP Mapping: 500 Internal Server Error
+ UNKNOWN = 2;
+
+ // The client specified an invalid argument. Note that this differs
+ // from `FAILED_PRECONDITION`. `INVALID_ARGUMENT` indicates arguments
+ // that are problematic regardless of the state of the system
+ // (e.g., a malformed file name).
+ //
+ // HTTP Mapping: 400 Bad Request
+ INVALID_ARGUMENT = 3;
+
+ // The deadline expired before the operation could complete. For operations
+ // that change the state of the system, this error may be returned
+ // even if the operation has completed successfully. For example, a
+ // successful response from a server could have been delayed long
+ // enough for the deadline to expire.
+ //
+ // HTTP Mapping: 504 Gateway Timeout
+ DEADLINE_EXCEEDED = 4;
+
+ // Some requested entity (e.g., file or directory) was not found.
+ //
+ // Note to server developers: if a request is denied for an entire class
+ // of users, such as gradual feature rollout or undocumented whitelist,
+ // `NOT_FOUND` may be used. If a request is denied for some users within
+ // a class of users, such as user-based access control, `PERMISSION_DENIED`
+ // must be used.
+ //
+ // HTTP Mapping: 404 Not Found
+ NOT_FOUND = 5;
+
+ // The entity that a client attempted to create (e.g., file or directory)
+ // already exists.
+ //
+ // HTTP Mapping: 409 Conflict
+ ALREADY_EXISTS = 6;
+
+ // The caller does not have permission to execute the specified
+ // operation. `PERMISSION_DENIED` must not be used for rejections
+ // caused by exhausting some resource (use `RESOURCE_EXHAUSTED`
+ // instead for those errors). `PERMISSION_DENIED` must not be
+ // used if the caller can not be identified (use `UNAUTHENTICATED`
+ // instead for those errors). This error code does not imply the
+ // request is valid or the requested entity exists or satisfies
+ // other pre-conditions.
+ //
+ // HTTP Mapping: 403 Forbidden
+ PERMISSION_DENIED = 7;
+
+ // The request does not have valid authentication credentials for the
+ // operation.
+ //
+ // HTTP Mapping: 401 Unauthorized
+ UNAUTHENTICATED = 16;
+
+ // Some resource has been exhausted, perhaps a per-user quota, or
+ // perhaps the entire file system is out of space.
+ //
+ // HTTP Mapping: 429 Too Many Requests
+ RESOURCE_EXHAUSTED = 8;
+
+ // The operation was rejected because the system is not in a state
+ // required for the operation's execution. For example, the directory
+ // to be deleted is non-empty, an rmdir operation is applied to
+ // a non-directory, etc.
+ //
+ // Service implementors can use the following guidelines to decide
+ // between `FAILED_PRECONDITION`, `ABORTED`, and `UNAVAILABLE`:
+ // (a) Use `UNAVAILABLE` if the client can retry just the failing call.
+ // (b) Use `ABORTED` if the client should retry at a higher level
+ // (e.g., when a client-specified test-and-set fails, indicating the
+ // client should restart a read-modify-write sequence).
+ // (c) Use `FAILED_PRECONDITION` if the client should not retry until
+ // the system state has been explicitly fixed. E.g., if an "rmdir"
+ // fails because the directory is non-empty, `FAILED_PRECONDITION`
+ // should be returned since the client should not retry unless
+ // the files are deleted from the directory.
+ //
+ // HTTP Mapping: 400 Bad Request
+ FAILED_PRECONDITION = 9;
+
+ // The operation was aborted, typically due to a concurrency issue such as
+ // a sequencer check failure or transaction abort.
+ //
+ // See the guidelines above for deciding between `FAILED_PRECONDITION`,
+ // `ABORTED`, and `UNAVAILABLE`.
+ //
+ // HTTP Mapping: 409 Conflict
+ ABORTED = 10;
+
+ // The operation was attempted past the valid range. E.g., seeking or
+ // reading past end-of-file.
+ //
+ // Unlike `INVALID_ARGUMENT`, this error indicates a problem that may
+ // be fixed if the system state changes. For example, a 32-bit file
+ // system will generate `INVALID_ARGUMENT` if asked to read at an
+ // offset that is not in the range [0,2^32-1], but it will generate
+ // `OUT_OF_RANGE` if asked to read from an offset past the current
+ // file size.
+ //
+ // There is a fair bit of overlap between `FAILED_PRECONDITION` and
+ // `OUT_OF_RANGE`. We recommend using `OUT_OF_RANGE` (the more specific
+ // error) when it applies so that callers who are iterating through
+ // a space can easily look for an `OUT_OF_RANGE` error to detect when
+ // they are done.
+ //
+ // HTTP Mapping: 400 Bad Request
+ OUT_OF_RANGE = 11;
+
+ // The operation is not implemented or is not supported/enabled in this
+ // service.
+ //
+ // HTTP Mapping: 501 Not Implemented
+ UNIMPLEMENTED = 12;
+
+ // Internal errors. This means that some invariants expected by the
+ // underlying system have been broken. This error code is reserved
+ // for serious errors.
+ //
+ // HTTP Mapping: 500 Internal Server Error
+ INTERNAL = 13;
+
+ // The service is currently unavailable. This is most likely a
+ // transient condition, which can be corrected by retrying with
+ // a backoff.
+ //
+ // See the guidelines above for deciding between `FAILED_PRECONDITION`,
+ // `ABORTED`, and `UNAVAILABLE`.
+ //
+ // HTTP Mapping: 503 Service Unavailable
+ UNAVAILABLE = 14;
+
+ // Unrecoverable data loss or corruption.
+ //
+ // HTTP Mapping: 500 Internal Server Error
+ DATA_LOSS = 15;
+}
\ No newline at end of file
diff --git a/buildstream/_protos/google/rpc/code_pb2.py b/buildstream/_protos/google/rpc/code_pb2.py
new file mode 100644
index 0000000000000000000000000000000000000000..e06dea194e1900c2fa91a09401395cf418b6b0ed
--- /dev/null
+++ b/buildstream/_protos/google/rpc/code_pb2.py
@@ -0,0 +1,133 @@
+# Generated by the protocol buffer compiler. DO NOT EDIT!
+# source: google/rpc/code.proto
+
+import sys
+_b=sys.version_info[0]<3 and (lambda x:x) or (lambda x:x.encode('latin1'))
+from google.protobuf.internal import enum_type_wrapper
+from google.protobuf import descriptor as _descriptor
+from google.protobuf import message as _message
+from google.protobuf import reflection as _reflection
+from google.protobuf import symbol_database as _symbol_database
+# @@protoc_insertion_point(imports)
+
+_sym_db = _symbol_database.Default()
+
+
+
+
+DESCRIPTOR = _descriptor.FileDescriptor(
+ name='google/rpc/code.proto',
+ package='google.rpc',
+ syntax='proto3',
+ serialized_options=_b('\n\016com.google.rpcB\tCodeProtoP\001Z3google.golang.org/genproto/googleapis/rpc/code;code\242\002\003RPC'),
+ serialized_pb=_b('\n\x15google/rpc/code.proto\x12\ngoogle.rpc*\xb7\x02\n\x04\x43ode\x12\x06\n\x02OK\x10\x00\x12\r\n\tCANCELLED\x10\x01\x12\x0b\n\x07UNKNOWN\x10\x02\x12\x14\n\x10INVALID_ARGUMENT\x10\x03\x12\x15\n\x11\x44\x45\x41\x44LINE_EXCEEDED\x10\x04\x12\r\n\tNOT_FOUND\x10\x05\x12\x12\n\x0e\x41LREADY_EXISTS\x10\x06\x12\x15\n\x11PERMISSION_DENIED\x10\x07\x12\x13\n\x0fUNAUTHENTICATED\x10\x10\x12\x16\n\x12RESOURCE_EXHAUSTED\x10\x08\x12\x17\n\x13\x46\x41ILED_PRECONDITION\x10\t\x12\x0b\n\x07\x41\x42ORTED\x10\n\x12\x10\n\x0cOUT_OF_RANGE\x10\x0b\x12\x11\n\rUNIMPLEMENTED\x10\x0c\x12\x0c\n\x08INTERNAL\x10\r\x12\x0f\n\x0bUNAVAILABLE\x10\x0e\x12\r\n\tDATA_LOSS\x10\x0f\x42X\n\x0e\x63om.google.rpcB\tCodeProtoP\x01Z3google.golang.org/genproto/googleapis/rpc/code;code\xa2\x02\x03RPCb\x06proto3')
+)
+
+_CODE = _descriptor.EnumDescriptor(
+ name='Code',
+ full_name='google.rpc.Code',
+ filename=None,
+ file=DESCRIPTOR,
+ values=[
+ _descriptor.EnumValueDescriptor(
+ name='OK', index=0, number=0,
+ serialized_options=None,
+ type=None),
+ _descriptor.EnumValueDescriptor(
+ name='CANCELLED', index=1, number=1,
+ serialized_options=None,
+ type=None),
+ _descriptor.EnumValueDescriptor(
+ name='UNKNOWN', index=2, number=2,
+ serialized_options=None,
+ type=None),
+ _descriptor.EnumValueDescriptor(
+ name='INVALID_ARGUMENT', index=3, number=3,
+ serialized_options=None,
+ type=None),
+ _descriptor.EnumValueDescriptor(
+ name='DEADLINE_EXCEEDED', index=4, number=4,
+ serialized_options=None,
+ type=None),
+ _descriptor.EnumValueDescriptor(
+ name='NOT_FOUND', index=5, number=5,
+ serialized_options=None,
+ type=None),
+ _descriptor.EnumValueDescriptor(
+ name='ALREADY_EXISTS', index=6, number=6,
+ serialized_options=None,
+ type=None),
+ _descriptor.EnumValueDescriptor(
+ name='PERMISSION_DENIED', index=7, number=7,
+ serialized_options=None,
+ type=None),
+ _descriptor.EnumValueDescriptor(
+ name='UNAUTHENTICATED', index=8, number=16,
+ serialized_options=None,
+ type=None),
+ _descriptor.EnumValueDescriptor(
+ name='RESOURCE_EXHAUSTED', index=9, number=8,
+ serialized_options=None,
+ type=None),
+ _descriptor.EnumValueDescriptor(
+ name='FAILED_PRECONDITION', index=10, number=9,
+ serialized_options=None,
+ type=None),
+ _descriptor.EnumValueDescriptor(
+ name='ABORTED', index=11, number=10,
+ serialized_options=None,
+ type=None),
+ _descriptor.EnumValueDescriptor(
+ name='OUT_OF_RANGE', index=12, number=11,
+ serialized_options=None,
+ type=None),
+ _descriptor.EnumValueDescriptor(
+ name='UNIMPLEMENTED', index=13, number=12,
+ serialized_options=None,
+ type=None),
+ _descriptor.EnumValueDescriptor(
+ name='INTERNAL', index=14, number=13,
+ serialized_options=None,
+ type=None),
+ _descriptor.EnumValueDescriptor(
+ name='UNAVAILABLE', index=15, number=14,
+ serialized_options=None,
+ type=None),
+ _descriptor.EnumValueDescriptor(
+ name='DATA_LOSS', index=16, number=15,
+ serialized_options=None,
+ type=None),
+ ],
+ containing_type=None,
+ serialized_options=None,
+ serialized_start=38,
+ serialized_end=349,
+)
+_sym_db.RegisterEnumDescriptor(_CODE)
+
+Code = enum_type_wrapper.EnumTypeWrapper(_CODE)
+OK = 0
+CANCELLED = 1
+UNKNOWN = 2
+INVALID_ARGUMENT = 3
+DEADLINE_EXCEEDED = 4
+NOT_FOUND = 5
+ALREADY_EXISTS = 6
+PERMISSION_DENIED = 7
+UNAUTHENTICATED = 16
+RESOURCE_EXHAUSTED = 8
+FAILED_PRECONDITION = 9
+ABORTED = 10
+OUT_OF_RANGE = 11
+UNIMPLEMENTED = 12
+INTERNAL = 13
+UNAVAILABLE = 14
+DATA_LOSS = 15
+
+
+DESCRIPTOR.enum_types_by_name['Code'] = _CODE
+_sym_db.RegisterFileDescriptor(DESCRIPTOR)
+
+
+DESCRIPTOR._options = None
+# @@protoc_insertion_point(module_scope)
diff --git a/buildstream/_protos/google/rpc/code_pb2_grpc.py b/buildstream/_protos/google/rpc/code_pb2_grpc.py
new file mode 100644
index 0000000000000000000000000000000000000000..a89435267cb22829c48fadd60cf5623a31dc7aa3
--- /dev/null
+++ b/buildstream/_protos/google/rpc/code_pb2_grpc.py
@@ -0,0 +1,3 @@
+# Generated by the gRPC Python protocol compiler plugin. DO NOT EDIT!
+import grpc
+