Add raise_ajax decorator to vispa.remote.

vispa/remote/__init__.py

@@ -34,3 +34,18 @@ class AjaxException(Exception):
 
         self.code  = code
         self.alert = alert
+
+
+def raise_ajax(fn):
+    """
+    Decorator that transforms raised exceptions into AjaxExceptions.
+    """
+    def wrapper(*args, **kwargs):
+        try:
+            return fn(*args, **kwargs)
+        except Exception as e:
+            if isinstance(e, AjaxException):
+                raise
+            else:
+                raise AjaxException(str(e))
+    return wrapper