Merge #16034: Fix performance regressions in the new BZ2File implementation.

Thanks to Victor Hooi for the bug report, and Serhiy Storchaka for the initial patch.

diff --cc Misc/NEWS
index 04751b710b1aeddbe9f5ef6a23111e00a1956f59,7bfa6498acaf79c455554e2c3cb805d8b1df6f71..0d6afecefe411171dc7969d20726adb27813b233
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -15,8 -13,9 +15,11 @@@ Core and Builtin
  Library
  -------
  
+ - Issue #16034: Fix performance regressions in the new BZ2File implementation.
+   Initial patch by Serhiy Storchaka.
+ 
 +- pty.spawn() now returns the child process status returned by os.waitpid().
 +
  - Issue #15756: subprocess.poll() now properly handles errno.ECHILD to
    return a returncode of 0 when the child has already exited or cannot
    be waited on.