core, frontends: fix invalid translatable strings.

Some f-strings where used in translatable text, this has been fixed by using explicit
`format()` call (using a script based on `tokenize`).

As tokenize messes with spaces, a reformating tool (`black`) has been applied to some
files afterwards.

sat/plugins/plugin_xep_0329.py

@@ -708,7 +708,8 @@ class XEP_0329(object):
                 )
             else:
                 log.warning(
-                    _(f"unexpected element, ignoring: {elt.toXml()}")
+                    _("unexpected element, ignoring: {elt}")
+                    .format(elt=elt.toXml())
                 )
                 continue
             files.append(file_data)