better msg when media sanity fails

anki/sync.py

@@ -703,10 +703,7 @@ class MediaSyncer(object):
         if c != s:
             # if the sanity check failed, force a resync
             self.col.media.forceResync()
-            raise Exception("""\
-Media sanity check failed. Please copy and paste the text below:\n%s\n%s""" %
-                            (c, s))
-        return "success"
+            return "sanityCheckFailed"
 
     def removed(self):
         return self.col.media.removed()

aqt/sync.py

@@ -114,6 +114,10 @@ Please visit AnkiWeb, upgrade your deck, then try again."""))
             self._clockOff()
         elif evt == "checkFailed":
             self._checkFailed()
+        elif evt == "mediaSanity":
+            showWarning(_("""\
+A problem occurred while syncing media. Please sync again and Anki will \
+correct the issue."""))
         elif evt == "noChanges":
             pass
         elif evt == "fullSync":
@@ -382,6 +386,8 @@ class SyncThread(QThread):
         ret = self.client.sync(self.mediaUsn)
         if ret == "noChanges":
             self.fireEvent("noMediaChanges")
+        elif ret == "sanityCheckFailed":
+            self.fireEvent("mediaSanity")
         else:
             self.fireEvent("mediaSuccess")