From 0de1f68962db3e8e41c2947fc3d19e7d500ef96f Mon Sep 17 00:00:00 2001
From: najuzilu <junaluzi@gmail.com>
Date: Thu, 8 Oct 2020 22:15:07 +0200
Subject: [PATCH] :bug: FIX: check during doctree-resolve if env has attribute

---
 sphinx_exercise/__init__.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sphinx_exercise/__init__.py b/sphinx_exercise/__init__.py
index 59be873..f724f32 100644
--- a/sphinx_exercise/__init__.py
+++ b/sphinx_exercise/__init__.py
@@ -313,6 +313,9 @@ def process(self, doctree: nodes.document, docname: str) -> None:
         # Traverse ref and numref nodes
         for node in doctree.traverse():
 
+            if not hasattr(self.env, "exercise_list"):
+                continue
+
             # If node type is ref
             if isinstance(node, nodes.reference):
                 labelid = self._get_refuri(node)