Another place where errors may arise during frame traversal (#240)

* Handle iteration errors during frame traversal

* Fixes as suggested by @untitaker

* Add explanatory comments

* Replace deprecated `render_to_response` with `render`

* Handle only list and tuple instances in `break_cycles()`

* Add comment to changes to `break_cycles()` logic

Author: leotrubach

sentry_sdk/utils.py

@@ -633,7 +633,9 @@ def break_cycles(obj, memo=None):
     try:
         if isinstance(obj, Mapping):
             return {k: break_cycles(v, memo) for k, v in obj.items()}
-        if isinstance(obj, Sequence) and not isinstance(obj, (text_type, bytes)):
+        if isinstance(obj, (list, tuple)):
+            # It is not safe to iterate over another sequence types as this may raise errors or
+            # bring undesired side-effects (e.g. Django querysets are executed during iteration)
             return [break_cycles(v, memo) for v in obj]
         return obj
     finally: