calcurse-caldav: Check response status

Bail out if the HTTP status code of any of the replies starts with a
digit other than 2.

Signed-off-by: Lukas Fleischer <lfleischer@calcurse.org>

contrib/caldav/calcurse-caldav.py

@@ -100,6 +100,11 @@ def remote_query(cmd, path, additional_headers, body):
     if not resp:
         return (None, None)
 
+    if resp.status - (resp.status % 100) != 200:
+        die(("The server at %s replied with HTTP status code %d (%s) " +
+             "while trying to access %s.") %
+            (hostname, resp.status, resp.reason, path))
+
     headers = resp.getheaders()
     body = resp.read().decode('utf-8')