Do not send empty mail

tracim/tracim/lib/email_fetcher.py

         #  if no from address for example) and catch it here
         while mails:
             mail = mails.pop()
+            body =  mail.get_body(
+                           use_html_parsing=self.use_html_parsing,
+                           use_txt_parsing=self.use_txt_parsing)
+            from_address = mail.get_from_address()
+
+            # don't create element for 'empty' mail
+            if not body:
+                logger.warning(
+                    self,
+                    'Mail from {} has not valable content'.format(
+                        from_address
+                    ),
+                )
+                continue
+
             msg = {'token': self.token,
-                   'user_mail': mail.get_from_address(),
+                   'user_mail': from_address,
                    'content_id': mail.get_key(),
                    'payload': {
-                       'content': mail.get_body(
-                           use_html_parsing=self.use_html_parsing,
-                           use_txt_parsing=self.use_txt_parsing),
+                       'content': body,
                    }}
             try:
                 logger.debug(

tracim/tracim/lib/email_processing/sanitizer.py

+import typing
 from bs4 import BeautifulSoup, Tag
 from tracim.lib.email_processing.sanitizer_config.attrs_whitelist import \
     ATTRS_WHITELIST
     """
 
     @classmethod
-    def sanitize(cls, html_body: str) -> str:
+    def sanitize(cls, html_body: str) -> typing.Optional[str]:
         soup = BeautifulSoup(html_body, 'html.parser')
         for tag in soup.findAll():
             if cls._tag_to_extract(tag):
                         del tag.attrs[attr]
             else:
                 tag.unwrap()
-        return str(soup)
+
+        if cls._is_content_empty(soup):
+            return None
+        else:
+            return str(soup)
+
+    @classmethod
+    def _is_content_empty(cls, soup):
+        img = soup.find('img')
+        txt = soup.get_text().replace('\n', '').strip()
+        return (not img and not txt)
 
     @classmethod
     def _tag_to_extract(cls, tag: Tag) -> bool: