Running Rally with Python 3.8

[dliappis]

Python 3.8 was released on Oct 14 2019.

This ticket tracks:

• evaluating compatibility with Python 3.8
• identifying necessary changes (depending on issues identified) to support 3.8

[dliappis]

1. The Python Elasticsearch-Client (version 7.0.5 that we are currently using) is compatible with Python 3.8.

2. Installing Thespian (version 3.9.3 when using Python 3.8 generates some non-fatal warnings

   Non fatal syntax warnings while installing Thespian 3.9.3 with Python 3.8.0

   warning: no files found matching '*.txt' under directory 'contrib'
       warning: no files found matching '*.txt' under directory 'examples'
       build/bdist.linux-x86_64/egg/thespian/runcommand.py:427: SyntaxWarning: "is" with a literal. Did you mean "=="?
       if outmark is 'normal' else
       build/bdist.linux-x86_64/egg/thespian/runcommand.py:429: SyntaxWarning: "is" with a literal. Did you mean "=="?
       if outmark is 'normal':
       build/bdist.linux-x86_64/egg/thespian/runcommand.py:431: SyntaxWarning: "is" with a literal. Did you mean "=="?
       elif outmark is 'error':
       zip_safe flag not set; analyzing archive contents...
       thespian.__pycache__.director.cpython-38: module references __file__
       thespian.__pycache__.director.cpython-38: module references __path__
       thespian.system.__pycache__.sourceLoader.cpython-38: module references __file__
       thespian.system.__pycache__.sourceLoader.cpython-38: module references __path__
       thespian.system.admin.__pycache__.adminCore.cpython-38: module references __file__
       /var/lib/jenkins/.local/lib/python3.8/site-packages/thespian-3.9.3-py3.8.egg/thespian/runcommand.py:427: SyntaxWarning: "is" with a literal. Did you mean "=="?
       if outmark is 'normal' else
       /var/lib/jenkins/.local/lib/python3.8/site-packages/thespian-3.9.3-py3.8.egg/thespian/runcommand.py:429: SyntaxWarning: "is" with a literal. Did you mean "=="?
       if outmark is 'normal':
       /var/lib/jenkins/.local/lib/python3.8/site-packages/thespian-3.9.3-py3.8.egg/thespian/runcommand.py:431: SyntaxWarning: "is" with a literal. Did you mean "=="?
       elif outmark is 'error':
       zip_safe flag not set; analyzing archive contents...
       zip_safe flag not set; analyzing archive contents...
   

3. make it38 works without issues.