FileNotFoundError: [WinError 2] python 3.4 post commit hook

processCommit.py script looks like:

cmd = 'C:\Program Files\VisualSVN Server\bin\svnlook changed %s -r %s' %   (repo, rev)
Line 15 -->**changed = subprocess.Popen(cmd,stdout=subprocess.PIPE).communicate()[0]**
cmd = 'C:\Program Files\VisualSVN Server\bin\svnlook info %s -r %s' % (repo, rev)

Error that I am getting after commit :

Error: post-commit hook failed (exit code 1) with output:  
Error: Traceback (most recent call last):  
Error:   File "D:\Repositories\IapAdmin\hooks\processCommit.py", line 15, in <module>  
Error:     changed = subprocess.Popen(cmd,stdout=subprocess.PIPE).communicate()[0]  
Error:   File "C:\Python34\lib\subprocess.py", line 859, in __init__  
Error:     restore_signals, start_new_session)  
Error:   File "C:\Python34\lib\subprocess.py", line 1112, in _execute_child  
Error:     startupinfo)  
Error: FileNotFoundError: [WinError 2] The system cannot find the file specified