Use set_exception instead of set_exception_info

set_exception_info method is only available in python2 backport of concurrent.futures, while set_exception method available everywhere.

Author: Roman Skurikhin

collapsing_thread_pool_executor/collapsing_thread_pool_executor.py

@@ -52,9 +52,8 @@ def run(self):
 
  try:
  result = self.fn(*self.args, **self.kwargs)
- except BaseException:
- e, tb = sys.exc_info()[1:]
- self.future.set_exception_info(e, tb)
+ except BaseException as exc:
+ self.future.set_exception(exc)
  else:
  self.future.set_result(result)