Removed code related to Python 2

• Removed code related to Python 2

Added support for python 3.8

• Added pyhton 3.8 support
• Removed support for django's versions below 2.2

Dropped Python 2.7 support

• Drop Python 2.7 support
• cleaned up dependencies

0.2.1

• Check DB connection atomicity before closing "dead" connections.

0.2.0

Have the start_user_task receiver close obsolete connections before starting the task.

0.1.9

• Fix issue where ordering attribute of the UserTaskArtifactAdmin and UserTaskStatusAdmin classes must be a tuple or a list but was a string.

0.1.8

• Make the model list views in the admin panel more useful.
• Routing Python dependency upgrades.

0.1.7

Make UserTaskArtifact.url a TextField with a URLValidator instead of a URLField.

0.1.6

• Upgrade requirements.
• Change max_length of UserTaskArtifact.url from 200 to 512.