Hastexo-xblock

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* [Enhancement] Continue SSH verification on EOFError
* [Enhancement] Also handle keystone HTTP exceptions
* [Bug fix] Fail if environment not found or template not provided

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* [Bug fix] Handle all exceptions when suspending or reaping
* [Bug fix] Don't suspend or reap stacks with no provider
* [Bug fix] Don't delete manually resumed stacks
* [Bug fix] Refresh database connection on every run

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* [Enhancement] Allow `launch_timeout` to be set per course
* [Enhancement] Allow CMS editing of ports, provider, tests
* [Enhancement] Wait for RDP connection
* [Enhancement] Deprecate custom XML parsing
* [Enhancement] Parse stack ports from XML
* [Enhancement] Handle all Heat HTTP exceptions

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* [Enhancement] Don't create records implicitly
* [Bug fix] Wait for commit on LaunchStackTask()
* [Bug fix] Reset `error_msg` on stack launch
* [Bug fix] Only update necessary fields
* [Bug fix] Update provider in real time
* [Bug fix] Implement proper locking of `get_user_stack_status`
* [Bug fix] Roll back race condition check

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* [Bug fix] Don't try to retrieve empty paths
* [Bug fix] Don't send reset request twice simultaneously
* [Bug fix] Avoid QuerySet cache
* [Bug fix] Avoid launch race condition
* [Bug fix] Don't update database from tasks.py
* [Bug fix] Stop browser timers on errors

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* [Enhancement] Multiple provider support
* [Enhancement] Bump XBlock 1.2 testing to version 1.2.2
* [Security fix] Bump paramiko version