refactor ServerUtilities.py

[belforte]

Should have three files

• what is used also in CRABClient, hopefully very little, which needs to stay py2/3 compat
  • create new file name here (e.g. constants !)
• what is used only in server, so can move to py3 only and rely on pylint when changing
• accept also that some code like encodeRequest can be duplicated or adapted to simpler use case and moved to ClientUtilities

[novicecpp]

Just random though from reviewing #7800

• Keep ServerUtilities.py for sharing code for both client and server.
• Move all utils.py files into single directory src/python/utils like wmcore does.
  • This way, we can move RucioUtils.py into utils/rucio/functions.py and move RucioActions.py to utils/rucio/actions.py.
  • Also, mark src/python/utils directory exclusive for servers (REST/TW/PUB).

[belforte]

I like this idea, thanks @novicecpp
@mapellidario please add your thoughts. I defer further cleanup to after we have finalized this. No hurry.

[belforte]

Increased priority since it is good to have a plan. Which we will implement slowly

[belforte]

hand to Vijay ?

[belforte]

I will introduce src/python/Utils now. But I prefer to have few/no subdirectories there at this time, since I expect a limited number of files and there will be several utilities in common between TW and Publisher.

[belforte]

pfff.. CRABServer/src/python/Utils clashes with WMCore/src/python/Utils see #8557 (comment)