Py3 + CKAN 2.9 support for catalog.data.gov

[adborden]

User Story

In order to run on a supported version of Python and reduce the friction preventing us from staying up to date with new CKAN versions, the core catalog.data.gov application should be compatible with CKAN2.9 and Python 3.

Acceptance Criteria

[ACs should be clearly demoable/verifiable whenever possible. Try specifying them using BDD.]

• GIVEN [a contextual precondition]
  [AND optionally another precondition]
  WHEN [a triggering event] happens
  THEN [a verifiable outcome]
  [AND optionally another verifiable outcome]

Background

CKAN 2.9 migration notes

Security Considerations (required)

[Any security concerns that might be implicated in the change. "None" is OK, just be explicit here!]

Sketch

• ckan db upgrade
• Upgrade Solr schema to CKAN 2.9
• Update who.ini
• Open additional issues for non-essential migration tasks
• Create another issue for the inventory app based on this one.

[mogul]

Dupe of #3401