Kokoro setup for building gRPC Python with Bazel

In preparation for #8079, new CI tests have to be added to Kokoro for
testing gRPC Python with Bazel.

python-dev has to installed so that Python.h headers are available for
building Cython code.

templates/tools/dockerfile/test/bazel/Dockerfile.template

@@ -28,6 +28,8 @@
     openjdk-8-jdk ${'\\'}
     vim
   
+  <%include file="../../python_deps.include"/>
+
   <%include file="../../bazel.include"/>
   
   RUN mkdir -p /var/local/jenkins

tools/dockerfile/test/bazel/Dockerfile

@@ -26,6 +26,22 @@ RUN apt-get update && apt-get -y install \
   openjdk-8-jdk \
   vim
 
+#====================
+# Python dependencies
+
+# Install dependencies
+
+RUN apt-get update && apt-get install -y \
+    python-all-dev \
+    python3-all-dev \
+    python-pip
+
+# Install Python packages from PyPI
+RUN pip install --upgrade pip==10.0.1
+RUN pip install virtualenv
+RUN pip install futures==2.2.0 enum34==1.0.4 protobuf==3.5.2.post1 six==1.10.0 twisted==17.5.0
+
+
 #========================
 # Bazel installation
 RUN echo "deb [arch=amd64] http://storage.googleapis.com/bazel-apt stable jdk1.8" > /etc/apt/sources.list.d/bazel.list

tools/internal_ci/linux/grpc_python_bazel_test.cfg

@@ -0,0 +1,23 @@
+# Copyright 2018 gRPC authors.
+#
+# 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.
+
+# Config file for the internal CI (in protobuf text format)
+
+# Location of the continuous shell script in repository.
+build_file: "grpc/tools/internal_ci/linux/grpc_bazel.sh"
+timeout_mins: 240
+env_vars {
+  key: "BAZEL_SCRIPT"
+  value: "tools/internal_ci/linux/grpc_python_bazel_test_in_docker.sh"
+}

tools/internal_ci/linux/grpc_python_bazel_test_in_docker.sh

@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+# Copyright 2018 gRPC authors.
+#
+# 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.
+#
+# Test full Bazel
+#
+# NOTE: No empty lines should appear in this file before igncr is set!
+set -ex -o igncr || set -ex
+
+mkdir -p /var/local/git
+git clone /var/local/jenkins/grpc /var/local/git/grpc
+(cd /var/local/jenkins/grpc/ && git submodule foreach 'cd /var/local/git/grpc \
+&& git submodule update --init --reference /var/local/jenkins/grpc/${name} \
+${name}')
+cd /var/local/git/grpc/test
+bazel test --spawn_strategy=standalone --genrule_strategy=standalone //src/python/...