+ status = "400 Bad request"
+ title = "Error!"
+ body = "Required parameter is missing!"
+
+else:
+ q = form['q'].value
+ try:
+ tree = parser.parse(q)
+ except LexError:
+ tree = None
+ if tree is None:
+ status = "400 Bad request"
+ title = "Error!"
+ body = "Bad query syntax!"
+
+response(title, body, status)