BatcaveClient: check for valid URL

modules/batcave/client.py

@@ -5,8 +5,12 @@ from urllib2 import urlopen, URLError
 
 
 class BatcaveClient(object):
-    def __init__(self, base_url):
-        self.base_url = base_url
+    def __init__(self, url):
+        assert url.startswith("http://") or url.startswith("https://"), \
+            "BATCAVE URL must use http(s) protocol"
+        assert url.endswith("/"), "BATCAVE URL must end with slash."
+
+        self.base_url = url
         self.logger = logging.getLogger('BATCAVE')
 
     def __load_response(self, url, error_context):