Consolidate listification of _package_versions.
Consolidate listification of _package_versions.

All uses but one of _package_versions want a list, and the last one
is not special in terms of memory footprint: just return a list from
_package_versions.

nthall/pip,prasaianooz/pip,erikrose/pip,dstufft/pip,zorosteven/pip,esc/pip,jmagnusson/pip,RonnyPfannschmidt/pip,wkeyword/pip,RonnyPfannschmidt/pip,zenlambda/pip,benesch/pip,fiber-space/pip,jythontools/pip,blarghmatey/pip,jamezpolley/pip,zvezdan/pip,atdaemon/pip,willingc/pip,caosmo/pip,alex/pip,blarghmatey/pip,chaoallsome/pip,jythontools/pip,dstufft/pip,ncoghlan/pip,squidsoup/pip,luzfcb/pip,fiber-space/pip,ncoghlan/pip,caosmo/pip,tdsmith/pip,harrisonfeng/pip,atdaemon/pip,pfmoore/pip,xavfernandez/pip,qbdsoft/pip,davidovich/pip,techtonik/pip,harrisonfeng/pip,KarelJakubec/pip,davidovich/pip,pfmoore/pip,ChristopherHogan/pip,sigmavirus24/pip,natefoo/pip,jasonkying/pip,mindw/pip,erikrose/pip,xavfernandez/pip,qbdsoft/pip,fiber-space/pip,yati-sagade/pip,pypa/pip,rouge8/pip,sigmavirus24/pip,erikrose/pip,yati-sagade/pip,zvezdan/pip,benesch/pip,James-Firth/pip,esc/pip,James-Firth/pip,atdaemon/pip,luzfcb/pip,haridsv/pip,squidsoup/pip,supriyantomaftuh/pip,willingc/pip,esc/pip,Gabriel439/pip,mujiansu/pip,tdsmith/pip,wkeyword/pip,yati-sagade/pip,pypa/pip,pradyunsg/pip,rbtcollins/pip,zenlambda/pip,tdsmith/pip,zvezdan/pip,h4ck3rm1k3/pip,natefoo/pip,davidovich/pip,ChristopherHogan/pip,rouge8/pip,wkeyword/pip,caosmo/pip,natefoo/pip,blarghmatey/pip,squidsoup/pip,supriyantomaftuh/pip,qbdsoft/pip,ChristopherHogan/pip,nthall/pip,mujiansu/pip,KarelJakubec/pip,jamezpolley/pip,benesch/pip,h4ck3rm1k3/pip,zenlambda/pip,jasonkying/pip,rbtcollins/pip,h4ck3rm1k3/pip,harrisonfeng/pip,RonnyPfannschmidt/pip,ncoghlan/pip,alex/pip,chaoallsome/pip,nthall/pip,jmagnusson/pip,jythontools/pip,Gabriel439/pip,luzfcb/pip,xavfernandez/pip,haridsv/pip,sbidoul/pip,techtonik/pip,KarelJakubec/pip,mujiansu/pip,Gabriel439/pip,zorosteven/pip,rouge8/pip,mindw/pip,willingc/pip,pradyunsg/pip,supriyantomaftuh/pip,sigmavirus24/pip,jamezpolley/pip,mindw/pip,chaoallsome/pip,dstufft/pip,zorosteven/pip,James-Firth/pip,alex/pip,prasaianooz/pip,prasaianooz/pip,haridsv/pip,techtonik/pip,rbtcollins/pip,jmagnusson/pip,jasonkying/pip,sbidoul/pip