Fix the most error-prone code style violations in the validator
Fix the most error-prone code style violations in the validator

Mainly replacing Python 1-era old-style classes by new-style ones and
phrasing membership tests as ‘x not in y’.

jjgao/cbioportal,shrumit/cbioportal-gsoc-final,bihealth/cbioportal,angelicaochoa/cbioportal,adamabeshouse/cbioportal,bihealth/cbioportal,angelicaochoa/cbioportal,mandawilson/cbioportal,kalletlak/cbioportal,mandawilson/cbioportal,onursumer/cbioportal,kalletlak/cbioportal,kalletlak/cbioportal,gsun83/cbioportal,inodb/cbioportal,cBioPortal/cbioportal,sheridancbio/cbioportal,pughlab/cbioportal,pughlab/cbioportal,sheridancbio/cbioportal,shrumit/cbioportal-gsoc-final,yichaoS/cbioportal,bihealth/cbioportal,mandawilson/cbioportal,onursumer/cbioportal,gsun83/cbioportal,inodb/cbioportal,IntersectAustralia/cbioportal,mandawilson/cbioportal,d3b-center/pedcbioportal,jjgao/cbioportal,shrumit/cbioportal-gsoc-final,zhx828/cbioportal,yichaoS/cbioportal,d3b-center/pedcbioportal,d3b-center/pedcbioportal,zhx828/cbioportal,pughlab/cbioportal,cBioPortal/cbioportal,sheridancbio/cbioportal,zhx828/cbioportal,angelicaochoa/cbioportal,onursumer/cbioportal,zhx828/cbioportal,gsun83/cbioportal,shrumit/cbioportal-gsoc-final,sheridancbio/cbioportal,zhx828/cbioportal,n1zea144/cbioportal,n1zea144/cbioportal,IntersectAustralia/cbioportal,bihealth/cbioportal,yichaoS/cbioportal,d3b-center/pedcbioportal,onursumer/cbioportal,inodb/cbioportal,cBioPortal/cbioportal,mandawilson/cbioportal,adamabeshouse/cbioportal,IntersectAustralia/cbioportal,cBioPortal/cbioportal,gsun83/cbioportal,pughlab/cbioportal,yichaoS/cbioportal,sheridancbio/cbioportal,mandawilson/cbioportal,kalletlak/cbioportal,onursumer/cbioportal,bihealth/cbioportal,yichaoS/cbioportal,jjgao/cbioportal,cBioPortal/cbioportal,jjgao/cbioportal,mandawilson/cbioportal,yichaoS/cbioportal,adamabeshouse/cbioportal,IntersectAustralia/cbioportal,bihealth/cbioportal,d3b-center/pedcbioportal,inodb/cbioportal,d3b-center/pedcbioportal,gsun83/cbioportal,sheridancbio/cbioportal,angelicaochoa/cbioportal,shrumit/cbioportal-gsoc-final,zhx828/cbioportal,IntersectAustralia/cbioportal,n1zea144/cbioportal,adamabeshouse/cbioportal,adamabeshouse/cbioportal,shrumit/cbioportal-gsoc-final,jjgao/cbioportal,adamabeshouse/cbioportal,pughlab/cbioportal,gsun83/cbioportal,jjgao/cbioportal,adamabeshouse/cbioportal,inodb/cbioportal,bihealth/cbioportal,angelicaochoa/cbioportal,kalletlak/cbioportal,pughlab/cbioportal,n1zea144/cbioportal,gsun83/cbioportal,onursumer/cbioportal,kalletlak/cbioportal,angelicaochoa/cbioportal,n1zea144/cbioportal,IntersectAustralia/cbioportal,shrumit/cbioportal-gsoc-final,angelicaochoa/cbioportal,inodb/cbioportal,n1zea144/cbioportal,IntersectAustralia/cbioportal,inodb/cbioportal,yichaoS/cbioportal,pughlab/cbioportal,zhx828/cbioportal,cBioPortal/cbioportal,kalletlak/cbioportal,jjgao/cbioportal,n1zea144/cbioportal,d3b-center/pedcbioportal