Fix "username" property on Windows 7 which, for certain processes, returns "None\None", in which case AccessDenied gets raised instead. This matches procexp behavior which fills such process with a "<access denied>" string.
Fix "username" property on Windows 7 which, for certain processes, returns "None\None", in which case AccessDenied gets raised instead. This matches procexp behavior which fills such process with a "<access denied>" string.

huson2012/psutil,anfedorov/psutil,PFZheng/psutil,creativewild/psutil,skyshe/psutil,djhaskin987/psutil,nmani1905/psutil,vmolsa/psutil,huson2012/psutil,end18/psutil,google-code-export/psutil,vmolsa/psutil,peter-hst/psutil,tigerneil/psutil,kiranvizru/psutil,AlanZatarain/psutil,kiranvizru/psutil,zhengzheng/psutil,tigerneil/psutil,Alwnikrotikz/psutil,stupidcache/psutil,tigerneil/psutil,djhaskin987/psutil,shiva21/psutil,end18/psutil,skyshe/psutil,vmolsa/psutil,vmolsa/psutil,end18/psutil,djhaskin987/psutil,kiranvizru/psutil,Alwnikrotikz/psutil,chjwang/psutil,PFZheng/psutil,tigerneil/psutil,google-code-export/psutil,peter-hst/psutil,stupidcache/psutil,jucapj/psutil,skyshe/psutil,stupidcache/psutil,kiranvizru/psutil,nmani1905/psutil,skyshe/psutil,huson2012/psutil,google-code-export/psutil,end18/psutil,jucapj/psutil,google-code-export/psutil,anfedorov/psutil,zhengzheng/psutil,chjwang/psutil,djhaskin987/psutil,marmolu/psutil,marmolu/psutil,creativewild/psutil,creativewild/psutil,shiva21/psutil,AlanZatarain/psutil