In Python, when running shutil.rmtree over a folder that contains a read-only file, the following exception is printed:

 File "C:\Python26\lib\shutil.py", line 216, in rmtree
   rmtree(fullname, ignore_errors, onerror)
 File "C:\Python26\lib\shutil.py", line 216, in rmtree
   rmtree(fullname, ignore_errors, onerror)
 File "C:\Python26\lib\shutil.py", line 216, in rmtree
   rmtree(fullname, ignore_errors, onerror)
 File "C:\Python26\lib\shutil.py", line 216, in rmtree
   rmtree(fullname, ignore_errors, onerror)
 File "C:\Python26\lib\shutil.py", line 216, in rmtree
   rmtree(fullname, ignore_errors, onerror)
 File "C:\Python26\lib\shutil.py", line 216, in rmtree
   rmtree(fullname, ignore_errors, onerror)
 File "C:\Python26\lib\shutil.py", line 216, in rmtree
   rmtree(fullname, ignore_errors, onerror)
 File "C:\Python26\lib\shutil.py", line 221, in rmtree
   onerror(os.remove, fullname, sys.exc_info())
 File "C:\Python26\lib\shutil.py", line 219, in rmtree
   os.remove(fullname)
WindowsError: [Error 5] Access is denied: 'build\\tcl\\tcl8.5\\msgs\\af.msg'

Looking in File Properties dialog I noticed that af.msg file is set to be read-only.

So the question is: what is the simplest workaround/fix to get around this problem - given that my intention is to do an equivalent of rm -rf build/ but on Windows? (without having to use third-party tools like unxutils or cygwin - as this code is targeted to be run on a bare Windows install with Python 2.6 w/ PyWin32 installed)