Jenkins gcloud deployment causes ImportError - google-app-engine

Question

I've set up a Jenkins instance in Google Compute Engine to build and deploy an App Engine Java project following this page from Google.
I've configured Jenkins to run the following shell command only when the Maven build succeeds: gcloud --project=decent-ellipse-843 preview app deploy target/*-SNAPSHOT/
When I attempt a build, the deployment fails with the following trace:
+ gcloud --project=decent-ellipse-843 preview app deploy target/backend-api-0.0.1-SNAPSHOT/
Traceback (most recent call last):
File "/usr/local/bin/../share/google/google-cloud-sdk/./lib/googlecloudsdk/gcloud/gcloud.py", line 183, in <module>
main()
File "/usr/local/bin/../share/google/google-cloud-sdk/./lib/googlecloudsdk/gcloud/gcloud.py", line 179, in main
_cli.Execute()
File "/usr/local/bin/../share/google/google-cloud-sdk/./lib/googlecloudsdk/calliope/cli.py", line 488, in Execute
post_run_hooks=self.__post_run_hooks)
File "/usr/local/bin/../share/google/google-cloud-sdk/./lib/googlecloudsdk/calliope/backend.py", line 1016, in Run
result = command_instance.Run(args)
File "/usr/local/bin/../share/google/google-cloud-sdk/./lib/googlecloudsdk/calliope/exceptions.py", line 86, in TryFunc
return func(*args, **kwargs)
File "/usr/local/share/google/google-cloud-sdk/lib/googlecloudsdk/appengine/app_commands/deploy.py", line 158, in Run
stage_dir = self.__MakeStagingDir(project, args, deployable)
File "/usr/local/share/google/google-cloud-sdk/lib/googlecloudsdk/appengine/app_commands/deploy.py", line 268, in __MakeStagingDir
java_app_update = appcfg_java.JavaAppUpdate(deployable, args)
File "/usr/local/share/google/google-cloud-sdk/platform/google_appengine/google/appengine/tools/appcfg_java.py", line 146, in __init__
self.app_engine_web_xml = self._ReadAppEngineWebXml()
File "/usr/local/share/google/google-cloud-sdk/platform/google_appengine/google/appengine/tools/appcfg_java.py", line 205, in _ReadAppEngineWebXml
parser=app_engine_web_xml_parser.AppEngineWebXmlParser)
File "/usr/local/share/google/google-cloud-sdk/platform/google_appengine/google/appengine/tools/appcfg_java.py", line 217, in _ReadAndParseXml
return parser().ProcessXml(file_handle.read())
File "/usr/local/share/google/google-cloud-sdk/platform/google_appengine/google/appengine/tools/app_engine_web_xml_parser.py", line 71, in ProcessXml
xml_root = ElementTree.fromstring(xml_str)
File "/usr/lib/python2.7/xml/etree/ElementTree.py", line 1300, in XML
parser = XMLParser(target=TreeBuilder())
File "/usr/lib/python2.7/xml/etree/ElementTree.py", line 1466, in __init__
"No module named expat; use SimpleXMLTreeBuilder instead"
ImportError: No module named expat; use SimpleXMLTreeBuilder instead
Build step 'Execute shell' marked build as failure
Finished: FAILURE
The Maven build is successful, and I can deploy the project by issuing the gcloud command manually.
Even when I run the exact same gcloud command from the same directory and under the same user (tomcat), the deployment succeeds without errors.
I have re-installed python and updated the Google Cloud SDK without any results.
The instance is running Python 2.7.3, Jenkins 1.598, JDK 7u76 and Maven 3.2.2.
I hope someone can help me out with this!

Answer 1

I ran into a similar issue running my jobs on the cloud-dev-python slave. The images are missing build tools that you may need in order to build and deploy properly. My solution was to connect to the docker image and install the tools manually the first time around.
# on docker host, connect to java image
CONTAINER_ID=$(docker ps | grep cloud-dev-java | awk '{print $1}');
docker exec -i -t $CONTAINER_ID bash
# on docker image, install crap to build lxml, etc
gcloud -q components update preview app && apt-get update \
&& apt-get install -y build-essential libz-dev libxml2-dev \
libxslt1-dev python-dev python-pip && apt-get autoremove
Give that a whirl and see if it helps. I'm currently stuck with the service account not authenticating even though it is set up properly...