Pickling Error On Python 3.8

[dchukhin]

When trying to do a deploy (fab deploy_serial:<my-project-name>,<my-environment-name>) from within a virtual environment with Python3.8.3, I get the following pickling error: AttributeError: Can't pickle local object '_execute.<locals>.inner'.

Looking deeper, this seems to be caused by fabric having a function _execute() that defines a nested function named inner() (https://github.com/mathiasertl/fabric/blob/master/fabric/tasks.py#L236), which is not picklable.

Some more information:

• the _execute() function named above has had a nested function for years, and this didn't cause deployment issues
• running the same deployment command in a virtual environment with Python3.7.8 succeeds

This leads me to suspect that something about Python3.8 causes this pickling error.

[tobiasmcnulty]

http://gael-varoquaux.info/programming/decoration-in-python-done-right-decorating-and-pickling.html