add extra test for pid_exists()
add extra test for pid_exists()

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