Image.py: remove some warnings from imagemagick stdout

    **** Warning: considering '0000000000 XXXXX n' as a free entry.

https://codeyarns.com/2014/03/10/free-entry-warning-with-ghostscript-and-imagemagick/

> This warning turns out to be from the Ghostscript program, which is used by
> ImageMagick internally to perform this format conversion. This page explains
> that this error has been fixed in a recent version of Ghostscript. I used a
> newer version of Ubuntu, that is 13.11, that had a newer version of gs and I
> was able to perform the format conversion. It still gave off the warning,
> but the conversion was done.

Image.py tells imagemagick to convert to stdout.
Warnings are also returned via stdout before actual rendering.

product/ERP5/Document/Image.py

@@ -34,6 +34,7 @@ import os
 import string
 import struct
 import subprocess
+import re
 from cStringIO import StringIO
 
 from AccessControl import ClassSecurityInfo
@@ -369,6 +370,9 @@ class Image(TextConvertableMixin, File, OFSImage):
         # XXX: The only portable way is to pass what stdin.write can accept,
         #      which is a string for PIPE.
         image, err = process.communicate(data)
+        # XXX Hack to remove some warnings from imagemagick stdout !
+        #     https://codeyarns.com/2014/03/10/free-entry-warning-with-ghostscript-and-imagemagick/
+        image = re.sub(r"^(   \*\*\*\* Warning: considering '0000000000 XXXXX n' as a free entry.\n)+", "", image)
     finally:
         del process
     if image: