test: use json response

src/node/api_clients/rest.py

@@ -28,4 +28,5 @@ class REST(BaseClient):
         return self.rest_call("post", "disperse-data", json.dumps(data))
 
     def send_get_range(self, query):
-        return self.rest_call("post", "da/get-range", json.dumps(query))
+        response = self.rest_call("post", "da/get-range", json.dumps(query))
+        return response.json()

src/steps/da.py

@@ -28,15 +28,13 @@ class StepsDataAvailability(StepsCommon):
 
     @allure.step
     def get_data_range(self, app_id, start, end):
-        response_bytes = []
+        response = []
         query = prepare_get_range_request(app_id, start, end)
         try:
-            response_bytes = self.node2.send_get_data_range_request(query)
+            response = self.node2.send_get_data_range_request(query)
         except Exception as ex:
             assert "Bad Request" in str(ex) or "Internal Server Error" in str(ex)
 
         # Extract data as a string for each index in the received order
-        parsed_data = []
-        for item in response_bytes.content:
-            parsed_data.append(item)
+        parsed_data = json.loads(response)
         return parsed_data