XML files must be open in binary mode for sax parser

The sax parser expect a byte stream, so we must open the file with the binary
mode. Also file_open should have a default encoding to None because encoding
should not be set in binary mode.

issue5313

trytond/modules/__init__.py

@@ -244,7 +244,7 @@ def load_module_graph(graph, pool, update=None, lang=None):
                 filename = filename.replace('/', os.sep)
                 logger.info('%s:loading %s', module, filename)
                 # Feed the parser with xml content:
-                with tools.file_open(OPJ(module, filename)) as fp:
+                with tools.file_open(OPJ(module, filename), 'rb') as fp:
                     tryton_parser.parse_xmlstream(fp)
 
             modules_todo.append((module, list(tryton_parser.to_delete)))

trytond/tools/misc.py

@@ -51,7 +51,7 @@ def exec_command_pipe(name, *args, **kwargs):
         stdout=subprocess.PIPE, env=child_env)
 
 
-def file_open(name, mode="r", subdir='modules', encoding='utf-8'):
+def file_open(name, mode="r", subdir='modules', encoding=None):
     """Open a file from the root dir, using a subdir folder."""
     from trytond.modules import EGG_MODULES
     if sys.version_info < (3,):