Proper handling overwriting readonly files

[Gfy]

Trying to reconstruct an SRR file, the following unexpected error can be seen when trying to overwrite a readonly file:

Z:\[test]\Anchorman.Unrated.DVDRiP.XViD-DEiTY>srr Anchorman.Unrated.DVDRiP.XViD-DEiTY.srr
SRR file created with pyReScene Auto 0.5.
Warning: File Z:\[test]\Anchorman.Unrated.DVDRiP.XViD-DEiTY\anchorman.unrated.dvdrip.xvid-deity.nfo already exists.
Do you wish to continue? (Y/N): y
Traceback (most recent call last):
  File "C:\pyReScene\rescene\srr.py", line 493, in main
    parser.exit(manage_srr(options, infolder, infiles, working_dir))
  File "C:\pyReScene\rescene\srr.py", line 265, in manage_srr
    options.volume is None, options.volume)
  File "C:\pyReScene\rescene\main.py", line 1114, in reconstruct
    _extract(block, _opath(block, extract_paths, out_folder))
  File "C:\pyReScene\rescene\main.py", line 222, in _extract
    with open(out_file, "wb") as out_stream:
IOError: [Errno 13] Permission denied: u'Z:\\[test]\\Anchorman.Unrated.DVDRiP.XViD-DEiTY\\anchorman.unrated.dvdrip.xvid-deity.nfo'
Unexpected Error: [Errno 13] Permission denied: u'Z:\\[test]\\Anchorman.Unrated.DVDRiP.XViD-DEiTY\\anchorman.unrated.dvdrip.xvid-deity.nfo'Recreating stored file: anchorman.unrated.dvdrip.xvid-deity.nfo

This can occur after copying files from optical media.

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