Issue #2780: Fix assertion installing with no cache.
Issue #2780: Fix assertion installing with no cache.

This was an oversight.

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