[modules/contrib/stock] handle urllib request exception

Handle exception that is raised when e.g. your network connection is
down.

bumblebee_status/modules/contrib/stock.py

@@ -56,7 +56,11 @@ class Module(core.module.Module):
                 self.__symbols
                 + "&fields=regularMarketPrice,currency,regularMarketChange"
             )
-            return urllib.request.urlopen(url).read().strip()
+            try:
+                return urllib.request.urlopen(url).read().strip()
+            except urllib.request.URLError:
+                logging.error("unable to open stock exchange url")
+                return None
         else:
             logging.error("unable to retrieve stock exchange rate")
             return None