fix(curriculum): acknowledge tracebacks in binary search tree (#54789)

Co-authored-by: Ilenia <26656284+ilenia-magoni@users.noreply.github.com>

curriculum/challenges/english/07-scientific-computing-with-python/learn-tree-traversal-by-building-a-binary-search-tree/65c646d4148ae3b2d1cbcac4.md

@@ -11,12 +11,14 @@ Note that, your search returns something like `80: <__main__.TreeNode object at
 
 To change that to print a useful value, define another method named `__str__` in the `TreeNode` class. It takes a single argument `self`.
 
+After defining `__str__` you'll get an exception in the console because the `__str__` method doesn't return anything yet. You'll work on the method body in the next step.
+
 # --hints--
 
 You should define a method `__str__` that takes a single argument `self`. Remember to use `pass`.
 
 ```js
-assert.match(code, /def\s+__str__\(\s*self\s*\)/);
+assert.match(code, /^(\s+)def\s+__init__.+?^\1def\s+__str__\(\s*self\s*\)\s*:\s*\n^\1\1pass/ms)
 ```
 
 

curriculum/challenges/english/07-scientific-computing-with-python/learn-tree-traversal-by-building-a-binary-search-tree/65c9ddd336596e30a4266a50.md

@@ -9,6 +9,8 @@ dashedName: step-31
 
 In the body of the `__str__` method, delete `pass` and return the result of calling the `str()` function with `self.key` as the argument.  This is the attribute of the current node object that stores the value associated with the node.
 
+After returning the result, you should see the exception disappear from the console and the output should now display the value of the `key` associated with the node.
+
 # --hints--
 
 You should remove the `pass` keyword from the `__str__` method.