checkpatch: correct a parsing issue

Occasionally, characters will be sent which violate the
ascii decoder's sense of propriety.  In fact, in-tree there are
a few such files (ex: tests/atlocal.in), and they cause an
exception to be raised when they are encountered.

Set the policy to ignore these cases.  This means these bytes are
omitted from the text stream during processing.

Signed-off-by: Aaron Conole <aconole@redhat.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>

utilities/checkpatch.py

@@ -252,7 +252,7 @@ def ovs_checkpatch_parse(text):
     is_co_author = re.compile(r'(\s*(Co-authored-by: )(.*))$',
                               re.I | re.M | re.S)
 
-    for line in text.decode().split('\n'):
+    for line in text.decode(errors='ignore').split('\n'):
         if current_file != previous_file:
             previous_file = current_file