Return 400, if the query string is not a dict

When we parse the json object that come in query string,
we expect to find a dict, but not bail out if that not the case.
So this will raise a 500.

This changes this and return 400, because the input is invalid.

Change-Id: I1a3b927cdfb3b554026306d65a46ed91635d073c
Closes-bug: #1423634

wsme/rest/json.py

@@ -274,6 +274,8 @@ def parse(s, datatypes, bodyarg, encoding='utf8'):
     else:
         kw = {}
         extra_args = []
+        if not isinstance(jdata, dict):
+            raise wsme.exc.ClientSideError("Request must be a JSON dict")
         for key in jdata:
             if key not in datatypes:
                 extra_args.append(key)

wsme/tests/test_restjson.py

@@ -339,6 +339,14 @@ class TestRestJson(wsme.tests.protocol.RestOnlyProtocolTestCase):
         j = parse('{"a": "2011-01-01"}', {'a': datetime.date}, False)
         assert isinstance(j['a'], datetime.date)
 
+    def test_invalid_root_dict_fromjson(self):
+        try:
+            parse('["invalid"]', {'a': ArrayType(str)}, False)
+            assert False
+        except Exception as e:
+            assert isinstance(e, ClientSideError)
+            assert e.msg == "Request must be a JSON dict"
+
     def test_invalid_list_fromjson(self):
         jlist = "invalid"
         try: