Update Python script to OMPython 4.0.0

[AnHeuermann]

Issue

OMPython 4 no longer has function FindBestOMCSession.

File \"/OpenModelicaLibraryTesting/testmodel.py\", line 8, in <module>
        from OMPython import FindBestOMCSession, OMCSession, OMCSessionZMQ
 ImportError: cannot import name 'FindBestOMCSession' from 'OMPython'

We need to fix OMPython to 3.6 or update the scripts to work with 4.0.

[AnHeuermann]

@adpro How are Python dependencies like OMPython managed for our nightly tests?
If #244 get's merged we need to update them.