resolve trailing slash on list_submissions

Author: rfreling

codepost/models/abstract/api_resource.py

@@ -289,7 +289,7 @@ def instance_endpoint_by_id(self, id=None):
                 pass
 
             # CASE 2: The class end point has not formatting parameter
-            return urljoin(self.class_endpoint, "{}".format(_id))
+            return urljoin(self.class_endpoint, "{}/".format(_id))
 
     @property
     def instance_endpoint(self):

codepost/models/assignments.py

@@ -116,7 +116,7 @@ def list_submissions(self, id=None, student=None, grader=None):
 
         id = self._get_id(id=id)
 
-        endpoint = "{}/submissions".format(self.instance_endpoint_by_id(id=id))
+        endpoint = "{}submissions".format(self.instance_endpoint_by_id(id=id))
         endpoint_params = {}
 
         if student != None: