TINKERPOP-1641 Kerberos support for python

[spmallette]

https://issues.apache.org/jira/browse/TINKERPOP-1641

This PR replaces #1285.

VOTE +1

[vtslab]

I agree with this comment on the original PR:
"I do think the hardcoded "3.5.0-SNAPSHOT" in docker-entrypoint.sh needs to be dynamically referenced."
From the docker/gremlin-server/Dockerfile.template a GREMLIN_SERVER_VERSION variable is available from the environment. So, the offending line in docker-entrypoint.sh should read:
java -cp /opt/gremlin-test/gremlin-test-${GREMLIN_SERVER_VERSION}-jar-with-dependencies.jar \
While testing this I found that docker/gremlin_server.sh did not run and I do not understand how it ever can have worked. Anyway, docker needs absolute paths for the mounts and I think the docker run line should read:

ABS_PROJECT_HOME=$(dirname $(realpath $0))/..
docker run ${TINKERPOP_TEST_DOCKER_OPTS} ${REMOVE_CONTAINER} -h gremlin-server-test -v "${HOME}"/.groovy:/root/.groovy \
    -v "${HOME}"/.m2:/root/.m2 -v "${ABS_PROJECT_HOME}"/gremlin-test/target:/opt/gremlin-test -ti tinkerpop:${BUILD_TAG} ${@}

If you want I can put it in a PR against branch TINKERPOP-1641

[spmallette]

I've pushed the changes you suggested. Docker looks better now.

VOTE +1

[vtslab]

Great
VOTE +1

[spmallette]

It was suggested to me separately that we look to enhance the Client API as we keep just expanding its construction with new keywords. No need to do it for this PR - I've created an issue for discussion:

https://issues.apache.org/jira/browse/TINKERPOP-2382

[spmallette]

@vtslab sorry this one is still not merged - i'd like to get #1299 in first then look to merging this.

[spmallette]

I rebased this now that #1299 merged but now i'm getting failures with docker builds. need to investigate that further. the spark failures seem common now on travis for some reason...they seem to take longer than the 50 minute limit despite us not adding any additional tests recently. probably need to look into that as well.

[spmallette]

Rebased this on master - had to add an extra commit to cover issues with the removal of the templating system for GLVs. Still have to look into the docker issues and travis/spark build problems.

[spmallette]

Docker problems seem resolved now for some reason. I wonder if I ran afoul of an out-of-date docker image. Travis failures around spark still seem spread about. Restarted some travis builds that failed.