Hastexo-xblock

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* [Bug fix] Fix XML parsing backward compatibility

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* [BACKWARD INCOMPATIBLE FOR GCP LABS ONLY] Encode GCP stack names
* [Enhancement] Provider stack listing
* [Enhancement] Reaper zombie destroyer
* [Enhancement] Add Python 3.7 test target

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* [Bug fix] Fix database logging
* [Enhancement] Improve suspender and reaper database logging

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* [Enhancement] Refactor OpenStack client wrappers
* [Enhancement] Multi-cloud support
* [Enhancement] Introduce Gcloud provider driver
* [Bug fix] Fix Python 2-isms
* [Enhancement] Configurable guacd settings
* [Enhancement] Add docker support for guacamole app
* [Enhancement] Bump keystoneauth1
* [Bug fix] Fix app label
* [Enhancement] Bump os-client-config
* [Bug fix] Àdd missing init parameters to OpenStack wrappers
* [Enhancement] Avoid known stack suspension failure states

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* [Enhancement] Progress check hints via stderr
* [Enhancement] Track XBlock-SDK master branch in test matrix
* [Bug fix] Python 3.6 compatibility
* [Enhancement] Managed package versions

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* [Enhancement] Improve learner-facing warning messages