PySCIPOpt/SCIP - isLPSolBasic() not in pyscipopt.scip.Model
Your assumption is correct: The pip version of PySCIPOpt was outdated and did not yet include the latest updates with respect to cutting plane separators. I just triggered a new release build (v.1.4.6) that should be available soon.
When in doubt, you can always build PySCIPOpt from source by running python setup.py install from within the project directory.
I developed a gomory cut for a LP problem (based on 'test-gomory.py' test file) which I could not manage to run. Finally, I copied the test file to check whether I'd the same trouble. Indeed I got the same message:
if not scip.isLPSolBasic():
AttributeError: 'pyscipopt.scip.Model' object has no attribute 'isLPSolBasic'
I have downloaded SCIPOptSuite 5.0.1 win64, set up path and installed pyscipiopt using pip on conda. 
I cannot figure what is wrong, except that I may have failed to install pyscipopt properly? Thank you for pointing me in the right direction.