Python "FutureWarnings" in EE2 Standards (#19)

As more production packages use Python, we are going to start seeing
Python "FutureWarning" messages in operational log files. Python
"FutureWarning" messages do not indicate a current problem with the
production code–they warn about a Python or Python package
incompatibility that may cause jobs to fail _when a future version of
Python or the Python library is used._

Python "FutureWarning" messages should be considered acceptable during
the EE2 Review process and in operational log files. Developers should
make an effort to address the underlying cause of "FutureWarning"
messages, when possible, to prevent jobs from failing in the future. I'd
like the EE2 Standards document updated to reflect this.

Please feel free to suggest changes to the wording that I used in this
PR. Thanks!

CC @JacobCarley-NOAA @aerorahul @JustinCooke-NCO

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Co-authored-by: alicia bentley <alicia.bentley@dlogin01.dogwood.wcoss2.ncep.noaa.gov>
Co-authored-by: alicia bentley <alicia.bentley@dlogin05.dogwood.wcoss2.ncep.noaa.gov>

Author: 3 people

docs/standards.rst

@@ -623,6 +623,7 @@ Please also observe the following points:
 * All packages that use Python scripts must specify a Python version through the module system, and must only call a Python executable that is from a module, not the system version.
 * "``module load python/${python_ver:?}``" or similar must be present in all job files that will lead to python script calls, where the python version is defined in the version file.
 * Python version must be at version 3 or higher.
+* Python “FutureWarning” messages indicate that a specific feature, function, or syntax that is currently being used will be changed or removed in a future version of Python or in a future version of a Python library. Python “FutureWarning” messages are acceptable messages in operations and should not be suppressed. Developers should make an effort to resolve “FutureWarning” messages, when possible, in order to prevent production jobs from failing in the future. 
 
 Reference `Appendix A: Workflow Examples`_ for commented examples of a version file, ecFlow script, J-job, ex-script, modulefile and makefile.