Tell the user to refresh the applet cache

[mockturtl]

When an applet update is available, clicking the update button gives a 404.

"An error occurred while trying to access the server. Please try again in a little while.
Details: HTTP Error 404: Not Found"

Spices.py#download

I've had a few reports from users who don't understand they need to click "Refresh list" before updating.

Maybe the error message should be more informative?

[mtwebster]

I'm not sure how this is even happening - the program doesn't know there's an update unless the user refreshes the list. So this shouldn't occur.

The only cause I could maybe see it happening is a user has version X, then later refreshes the list and sees version Y available but doesn't update. In the meantime, you update to version Z, then the user tries to update, with an outdated cache that still points to version Y.

[dalcde]

This also happens when you try to install applets without refreshing the cache list

[coryhilliard]

Dalcde is right. You need to refresh list first.

[jaszhix]

I recently reproduced this issue, I am unable to update an applet I published recently. It does say an update is available, but refreshing the app, or restarting Cinnamon doesn't help. My guess is side-loading the applet from another source is causing it. Someone opened an issue on my applet's repo saying they were able to reproduce it.

I'm using Cinnamon 3.0.7 on Mint 18.

[NikoKrause]

This has changed in Cinnamon 3.6.
If the cache hasn't been refreshed in a while, you'll get a notification to refresh the cache first.