Add python lint tests.

[nanliu]

This change is 

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[k8s-ci-robot]

Hi @nanliu. Thanks for your PR.

I'm waiting for a kubernetes or tensorflow member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[nanliu]

Fixes #53

[coveralls]

Coverage remained the same at 31.746% when pulling 6384366 on nanliu:ci into 330eb92 on tensorflow:master.

[jlewi]

Thanks for the contribution. We already run pylint in prow. And I think we are already running gotomelinter in travis. What is the remaining work to do with fix lint?

[nanliu]

Ah, I wasn't aware of that. If it's no longer an issue feel free to close the PR and issue. I was doing something quick to check if my cla is working. Looks like I have to go track down some stuff on my end with our corporate cla.

[jimexist]

can we please use 3.6?

[nanliu]

After toggling it, I just remember the lint results are not very happy in 3.6 with a bunch of deprecation warnings, so I assumed the project was set to 2.7.

[jlewi]

I took a look at #53 and added some notes about what's missing.

For py it looks like we are missing pep8 check.

If you wanted to add pep8 check you could add it to our existing run_lint function
https://github.com/tensorflow/k8s/blob/master/py/py_checks.py#L18

That way it would be automatically invoked by prow and reported in prow (as opposed to using travis).

markdown autoformatting would be super nice as well. I think I'm seeing a lot of spurious changes in markdown PRs because everyone formats files differently. So would be really nice to start defining some standard conventions to cut this down.

[nanliu]

I signed it!