make it a bit clearer where an exception was thrown

util/eval.py

@@ -1,8 +1,11 @@
 # based on https://stackoverflow.com/a/39381428
 # Parses and executes a block of Python code, and returns the eval result of the last statement
 
+from concrete_syntax.common import indent
+
 import ast
 def exec_then_eval(code, _globals={}, _locals={}):
+    try:
         block = ast.parse(code, mode='exec')
         # assumes last node is an expression
         last = ast.Expression(block.body.pop().value)
@@ -11,12 +14,20 @@ def exec_then_eval(code, _globals={}, _locals={}):
             **_globals,
         }
         exec(compile(block, '<string>', mode='exec'), extended_globals, _locals)
-    return eval(compile(last, '<string>', mode='eval'), extended_globals, _locals)
+        result = eval(compile(last, '<string>', mode='eval'), extended_globals, _locals)
+        return result
+    except Exception as e:
+        e.add_note("In the following user code fragment:\n"+indent(code, 4))
+        raise
 
 def simply_exec(code, _globals={}, _locals={}):
+    try:
         block = ast.parse(code, mode='exec')
         extended_globals = {
             '__builtins__': __builtins__,
             **_globals,
         }
         exec(compile(block, '<string>', mode='exec'), extended_globals, _locals)
+    except Exception as e:
+        e.add_note("In the following user code fragment:\n"+indent(code, 4))
+        raise