If we cant decode using the body charset, try to decode using utf8. (#4)

If we can't decode using the body charset, try to decode using utf8.
Change the way we get the cahrset.

Task #159072

utils.py

@@ -3,10 +3,12 @@ import bleach
 def render_email(eml):
     body = eml.get_body(['html', 'plain'])
     if body:
-        charset = body.get_content_charset()
-        if not charset:
-            charset = 'utf-8'
-        html = body.get_payload(decode=True).decode(charset)
+        charset = body.get_content_charset('utf-8')
+        try:
+            html = body.get_payload(decode=True).decode(charset)
+        except:
+            # If the charset returns an error, try utf-8
+            html = body.get_payload(decode=True).decode('utf-8')
     else:
         html = ''
     images = {}