i18n: leave out entries which contain only a rst directive

This prevents the danger of translating entries like ".. note::"

i18n/posplit

@@ -55,6 +55,9 b' if __name__ == "__main__":'
                 newentry = mkentry(entry, delta, msgid, msgstr)
                 mdirective = findd.match(msgid)
                 if mdirective:
+                    if not msgid[mdirective.end():].rstrip():
+                        # only directive, nothing to translate here
+                        continue
                     directive = mdirective.group(1)
                     comment = 'do not translate: .. %s::' % directive
                     if not newentry.comment: