support large svg conversion

An error is thrown when convert a large svg file

File "<portal_components/mixin.erp5.DocumentMixin>", line 80, in convert                       
    result = self._convert(format, **kw)                                                         
  File "<portal_components/document.erp5.Image>", line 306, in _convert                          
    mime, image = self._makeDisplayPhoto(crop=crop, **kw)                                        
  File "<portal_components/document.erp5.Image>", line 437, in _makeDisplayPhoto                 
    crop))                                                                                       
  File "<portal_components/document.erp5.Image>", line 417, in _getDisplayData                   
    return self._resize(quality, width, height, format, resolution, frame, crop)                 
  File "<portal_components/document.erp5.Image>", line 377, in _resize                           
    data = transformUrlToDataURI(data)                                                           
  File "<portal_components/module.erp5.ImageUtil>", line 47, in transformUrlToDataURI            
    root = etree.fromstring(content)                                                             
  File "src/lxml/lxml.etree.pyx", line 3213, in lxml.etree.fromstring (src/lxml/lxml.etree.c:7901
0)                                                                                               
  File "src/lxml/parser.pxi", line 1848, in lxml.etree._parseMemoryDocument (src/lxml/lxml.etree.
c:118341)                                                                                        
  File "src/lxml/parser.pxi", line 1736, in lxml.etree._parseDoc (src/lxml/lxml.etree.c:117021)  
  File "src/lxml/parser.pxi", line 1102, in lxml.etree._BaseParser._parseDoc (src/lxml/lxml.etree
.c:111265)                                                                                       
  File "src/lxml/parser.pxi", line 595, in lxml.etree._ParserContext._handleParseResultDoc (src/l
xml/lxml.etree.c:105109)                                                                         
  File "src/lxml/parser.pxi", line 706, in lxml.etree._handleParseResult (src/lxml/lxml.etree.c:1
06817)                                                                                           
  File "src/lxml/parser.pxi", line 635, in lxml.etree._raiseParseError (src/lxml/lxml.etree.c:105
671)                                                                                             
XMLSyntaxError: internal error: Huge input lookup, line 81, column 204898 (line 81)