Fix gzip compression on Python 2

Author: peace-maker

pwnlib/tubes/tube.py

@@ -1168,7 +1168,11 @@ def upload_manually(self, data, target_path = './payload', prompt = b'$', chunk_
             compressed_path = target_path + '.xz'
         elif compression_mode == 'gzip':
             import gzip
-            compressed_data = gzip.compress(data, compresslevel=9)
+            from six import BytesIO
+            f = BytesIO()
+            with gzip.GzipFile(fileobj=f, mode='wb', compresslevel=9) as g:
+                g.write(data)
+            compressed_data = f.getvalue()
             compressed_path = target_path + '.gz'
         else:
             compressed_path = target_path