Prevent encoding error in headers when download a file

tracim/tracim/controllers/content.py

 from tracim.lib import CST
 from tracim.lib.base import BaseController
 from tracim.lib.base import logger
-from tracim.lib.utils import SameValueError
+from tracim.lib.utils import SameValueError, get_valid_header_file_name
 from tracim.lib.content import ContentApi
 from tracim.lib.helpers import convert_id_into_instances
 from tracim.lib.predicates import current_user_is_reader
             tg.response.headers['Content-type'] = str(revision_to_send.file_mimetype)
 
         tg.response.headers['Content-Type'] = content_type
-        tg.response.headers['Content-Disposition'] = str('attachment; filename="{}"'.format(revision_to_send.file_name))
+        file_name = get_valid_header_file_name(revision_to_send.file_name)
+        tg.response.headers['Content-Disposition'] = \
+            str('attachment; filename="{}"'.format(file_name))
         return revision_to_send.file_content
 
 

tracim/tracim/lib/utils.py

             title=resp.title,
             comment=resp.comment,
         )
+
+
+def get_valid_header_file_name(file_name: str) -> str:
+    """
+    :param file_name: file name to test
+    :return: Return given string if compatible to header encoding, or
+    download.ext if not.
+    """
+    try:
+        file_name.encode('iso-8859-1')
+        return file_name
+    except UnicodeEncodeError:
+        split_file_name = file_name.split('.')
+        if len(split_file_name) > 1:  # If > 1 so file have extension
+            return 'download.{0}'.format(split_file_name[-1])
+        return 'download'