fix: Python 3 urlencode (#5082)

The urllib.urlencode() function is now urllib.parse.urlencode()
diff --git a/tools/travis/box-upload.py b/tools/travis/box-upload.py
index 6152fd9..fad5039 100755
--- a/tools/travis/box-upload.py
+++ b/tools/travis/box-upload.py
@@ -44,7 +44,7 @@
         remote_file = remote_file[1:]
 
     url = "http://DamCYhF8.mybluemix.net/upload?%s" % \
-        urllib.urlencode({"name": remote_file})
+        urllib.parse.urlencode({"name": remote_file})
 
     r = requests.post(url,
             headers={"Content-Type": "application/gzip"},