Travis: Retry dependency installation
Travis: Retry dependency installation

We're getting lots of spurious checksum failures that are preventing the tests
from running. I hope this makes that situation less common.

SusannaMaria/beets,kareemallen/beets,Andypsamp/CODfinalJUNIT,untitaker/beets,YetAnotherNerd/beets,madmouser1/beets,multikatt/beets,MyTunesFreeMusic/privacy-policy,m-urban/beets,mried/beets,Dishwishy/beets,MyTunesFreeMusic/privacy-policy,swt30/beets,gabrielaraujof/beets,SusannaMaria/beets,randybias/beets,randybias/beets,Kraymer/beets,shamangeorge/beets,Andypsamp/CODfinalJUNIT,jackwilsdon/beets,marcuskrahl/beets,LordSputnik/beets,MyTunesFreeMusic/privacy-policy,sampsyo/beets,untitaker/beets,SusannaMaria/beets,YetAnotherNerd/beets,ruippeixotog/beets,beetbox/beets,jcoady9/beets,Kraymer/beets,m-urban/beets,pkess/beets,PierreRust/beets,shamangeorge/beets,lightwang1/beets,mried/beets,multikatt/beets,pkess/beets,xsteadfastx/beets,dfc/beets,ruippeixotog/beets,ibmibmibm/beets,sampsyo/beets,tima/beets,marcuskrahl/beets,arabenjamin/beets,gabrielaraujof/beets,drm00/beets,ibmibmibm/beets,ttsda/beets,moodboom/beets,Andypsamp/CODfinalJUNIT,ttsda/beets,ttsda/beets,mathstuf/beets,shanemikel/beets,jackwilsdon/beets,beetbox/beets,drm00/beets,LordSputnik/beets,jmwatte/beets,PierreRust/beets,jmwatte/beets,drm00/beets,Dishwishy/beets,artemutin/beets,mosesfistos1/beetbox,moodboom/beets,multikatt/beets,Freso/beets,lengtche/beets,kelvinhammond/beets,swt30/beets,arabenjamin/beets,mathstuf/beets,imsparsh/beets,m-urban/beets,shanemikel/beets,diego-plan9/beets,Andypsamp/CODjunit,kelvinhammond/beets,swt30/beets,shamangeorge/beets,madmouser1/beets,artemutin/beets,SusannaMaria/beets,kelvinhammond/beets,Freso/beets,sampsyo/beets,sadatay/beets,jackwilsdon/beets,kareemallen/beets,randybias/beets,swt30/beets,asteven/beets,mosesfistos1/beetbox,untitaker/beets,xsteadfastx/beets,parapente/beets,dfc/beets,asteven/beets,ibmibmibm/beets,parapente/beets,imsparsh/beets,mathstuf/beets,ruippeixotog/beets,kelvinhammond/beets,kareemallen/beets,Dishwishy/beets,dfc/beets,dfc/beets,kareemallen/beets,lightwang1/beets,gabrielaraujof/beets,PierreRust/beets,sadatay/beets,asteven/beets,YetAnotherNerd/beets,imsparsh/beets,shanemikel/beets,madmouser1/beets,Dishwishy/beets,lengtche/beets,xsteadfastx/beets,moodboom/beets,imsparsh/beets,tima/beets,MyTunesFreeMusic/privacy-policy,parapente/beets,lightwang1/beets,Freso/beets,m-urban/beets,multikatt/beets,diego-plan9/beets,gabrielaraujof/beets,jcoady9/beets,moodboom/beets,Andypsamp/CODjunit,Kraymer/beets,jmwatte/beets,PierreRust/beets,tima/beets,Andypsamp/CODfinalJUNIT,ibmibmibm/beets,jmwatte/beets,pkess/beets,parapente/beets,drm00/beets,ruippeixotog/beets,diego-plan9/beets,ttsda/beets,Kraymer/beets,mathstuf/beets,marcuskrahl/beets,arabenjamin/beets,mried/beets,artemutin/beets,Freso/beets,beetbox/beets,sadatay/beets,arabenjamin/beets,tima/beets,beetbox/beets,Andypsamp/CODfinalJUNIT,artemutin/beets,marcuskrahl/beets,lengtche/beets,Andypsamp/CODjunit,Andypsamp/CODjunit,untitaker/beets,mried/beets,LordSputnik/beets,lightwang1/beets,shamangeorge/beets,asteven/beets,YetAnotherNerd/beets,randybias/beets,shanemikel/beets,Andypsamp/CODjunit,madmouser1/beets,sampsyo/beets,mosesfistos1/beetbox,xsteadfastx/beets,mosesfistos1/beetbox,LordSputnik/beets,lengtche/beets,jcoady9/beets,jcoady9/beets,diego-plan9/beets,jackwilsdon/beets,sadatay/beets,pkess/beets