Fixed bug when running subset of testcases
Fixed bug when running subset of testcases

Happens when invoking `tox -e py27 test.test_ui` directly.
`os.environ.get('HOME')` seems to return None and raises an Exception
in tearDown of class

mried/beets,jackwilsdon/beets,artemutin/beets,parapente/beets,Freso/beets,jcoady9/beets,Kraymer/beets,madmouser1/beets,artemutin/beets,ibmibmibm/beets,swt30/beets,xsteadfastx/beets,ibmibmibm/beets,diego-plan9/beets,Freso/beets,pkess/beets,artemutin/beets,SusannaMaria/beets,mried/beets,ibmibmibm/beets,beetbox/beets,jackwilsdon/beets,MyTunesFreeMusic/privacy-policy,SusannaMaria/beets,sampsyo/beets,beetbox/beets,artemutin/beets,pkess/beets,MyTunesFreeMusic/privacy-policy,mried/beets,jcoady9/beets,SusannaMaria/beets,Freso/beets,swt30/beets,madmouser1/beets,jcoady9/beets,jackwilsdon/beets,MyTunesFreeMusic/privacy-policy,sampsyo/beets,mosesfistos1/beetbox,lengtche/beets,Freso/beets,parapente/beets,xsteadfastx/beets,xsteadfastx/beets,pkess/beets,mosesfistos1/beetbox,shamangeorge/beets,diego-plan9/beets,diego-plan9/beets,ibmibmibm/beets,xsteadfastx/beets,beetbox/beets,parapente/beets,Kraymer/beets,Kraymer/beets,diego-plan9/beets,shamangeorge/beets,sampsyo/beets,madmouser1/beets,shamangeorge/beets,MyTunesFreeMusic/privacy-policy,swt30/beets,lengtche/beets,jcoady9/beets,madmouser1/beets,mosesfistos1/beetbox,mried/beets,lengtche/beets,pkess/beets,lengtche/beets,sampsyo/beets,mosesfistos1/beetbox,Kraymer/beets,SusannaMaria/beets,beetbox/beets,jackwilsdon/beets,shamangeorge/beets,parapente/beets,swt30/beets