Patch #1110248: SYNC_FLUSH the zlib buffer for GZipFile.flush.

Partially fixes #1110242.

Lib/gzip.py

@@ -331,7 +331,10 @@ class GzipFile:
             return
         self.close()
 
-    def flush(self):
+    def flush(self,zlib_mode=zlib.Z_SYNC_FLUSH):
+        if self.mode == WRITE:
+           # Ensure the compressor's buffer is flushed
+           self.fileobj.write(self.compress.flush(zlib_mode))
         self.fileobj.flush()
 
     def fileno(self):

Misc/NEWS

@@ -59,6 +59,8 @@ Extension Modules
 Library
 -------
 
+- Patch #1110248: SYNC_FLUSH the zlib buffer for GZipFile.flush.
+
 - Patch #1107973: Allow to iterate over the lines of a tarfile.ExFileObject.
 
 - Patch #1104111: Alter setup.py --help and --help-commands.