re-apply traceback patches

Author: timfel

graalpython/lib-python/3/traceback.py

@@ -566,13 +566,18 @@ def format(self, *, chain=True):
         """
         if chain:
             if self.__cause__ is not None:
-                yield from self.__cause__.format(chain=chain)
+                # TODO(ls): revert this loop to "yield from"
+                for __x in self.__cause__.format(chain=chain): yield __x
                 yield _cause_message
             elif (self.__context__ is not None and
                 not self.__suppress_context__):
-                yield from self.__context__.format(chain=chain)
+                # TODO(ls): revert this loop to "yield from"
+                for __x in self.__context__.format(chain=chain): yield __x
                 yield _context_message
         if self.exc_traceback is not None:
             yield 'Traceback (most recent call last):\n'
-        yield from self.stack.format()
-        yield from self.format_exception_only()
+        # TODO(ls): revert this loop to "yield from"
+        for __x in self.stack.format(): yield __x
+        # TODO(ls): revert this loop to "yield from"
+        for __x in self.format_exception_only(): yield __x
+