updated the weather() sample function, closes #580

- increase the curl timeout to 2 seconds
- use curl -f -s instead of redirecting stderr to /dev/null
- print an empty line in case curl is not available or exists in error,
  which should prevent tmux from displaying <... not ready>

.tmux.conf.local

@@ -415,8 +415,8 @@ tmux_conf_uninstall_plugins_on_reload=true
 #
 # # /!\ do not "uncomment" the functions: the leading "# " characters are needed
 #
-# weather() {
-#   curl -m 1 wttr.in?format=3 2>/dev/null
+# weather() {                                         # see https://github.com/chubin/wttr.in#one-line-output
+#   curl -f -s -m 2 'wttr.in?format=3' || printf '\n' # /!\ make sure curl is installed
 #   sleep 900                                         # sleep for 15 minutes, throttle network requests whatever the value of status-interval
 # }
 #