Clearly use html.parser as parser

tracim/tracim/lib/email_processing/models.py

         # INFO - G.M - 2017-12-01 - Override part_type is elem has no content.
         # Choose last elem part_type instead of the proposed one.
         if len(self._list) > 0:
-            txt = BeautifulSoup(value.text).get_text().replace('\n','').strip()
+            txt = BeautifulSoup(value.text, 'html.parser').get_text()
+            txt = txt.replace('\n', '').strip()
             if not txt:
                 value.part_type = self._list[-1].part_type
         BodyMailParts._check_value(value)

tracim/tracim/tests/library/test_email_body_parser.py

         assert HtmlMailQuoteChecker._is_standard_quote(main_elem) is True
 
     def test_unit__is_standard_quote_no(self):
-        soup = BeautifulSoup('<a></a>')
+        soup = BeautifulSoup('<a></a>', 'html.parser')
         main_elem = soup.find()
         assert HtmlMailQuoteChecker._is_standard_quote(main_elem) is False
 
         assert HtmlMailQuoteChecker._is_thunderbird_quote(main_elem) is True
 
     def test_unit__is_thunderbird_quote_no(self):
-        soup = BeautifulSoup('<div class="nothing"></div>')
+        soup = BeautifulSoup('<div class="nothing"></div>', 'html.parser')
         main_elem = soup.find()
         assert HtmlMailQuoteChecker._is_thunderbird_quote(main_elem) is False