Make trace and doctest play nice together (issue 1429818).  Will backport.
diff --git a/Lib/trace.py b/Lib/trace.py
index 364e3f7..3f00605 100644
--- a/Lib/trace.py
+++ b/Lib/trace.py
@@ -286,6 +286,8 @@
             # skip some "files" we don't care about...
             if filename == "<string>":
                 continue
+            if filename.startswith("<doctest "):
+                continue
 
             if filename.endswith((".pyc", ".pyo")):
                 filename = filename[:-1]