SDK - Travis configuration for Python 3.5 and 3.7

[kvalev]

This change is 

[k8s-ci-robot]

Hi @kvalev. Thanks for your PR.

I'm waiting for a kubeflow 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.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[kvalev]

/assign @paveldournov

[Ark-kun]

/lgtm

[Ark-kun]

Thanks improving our dev test infra!

[Ark-kun]

/cc @IronPan

[Ark-kun]

/cc @IronPan Friendly ping

[k8s-ci-robot]

@Ark-kun: GitHub didn't allow me to request PR reviews from the following users: Friendly, ping.

Note that only kubeflow members and repo collaborators can review this PR, and authors cannot review their own PRs.

In response to this:

/cc @IronPan Friendly ping

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[IronPan]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: IronPan

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[Ark-kun]

/test kubeflow-pipeline-sample-test