Issue #16244: Merged change from 3.2.

diff --cc Lib/logging/handlers.py
index 2918360dc144f5e3c4821fe836fa4c6a694733de,8349d3a7fb906f156ef53e9e8c2b0e31e69d5ef4..f286cd61d4496c696ed568a91c75c00b7a19c80a
--- 1/Lib/logging/handlers.py
--- 2/Lib/logging/handlers.py
+++ b/Lib/logging/handlers.py
@@@ -168,11 -133,10 +168,10 @@@ class RotatingFileHandler(BaseRotatingH
                      if os.path.exists(dfn):
                          os.remove(dfn)
                      os.rename(sfn, dfn)
 -            dfn = self.baseFilename + ".1"
 +            dfn = self.rotation_filename(self.baseFilename + ".1")
              if os.path.exists(dfn):
                  os.remove(dfn)
 -            os.rename(self.baseFilename, dfn)
 +            self.rotate(self.baseFilename, dfn)
-         self.mode = 'w'
          self.stream = self._open()
  
      def shouldRollover(self, record):