Problem in apt-get Ubuntu 14.04

Error while updating ubuntu system. (sudo apt-get update)

W: Failed to fetch https://dl.bintray.com/sbt/debian/Packages  Received HTTP code 403 from proxy after CONNECT

E: Some index files failed to download. They have been ignored, or old ones used instead

Solution:
Step 1: check package in etc/apt/source.list
 if found
     Comment the particular package.
else
   Step 2: 
       a.  got to /etc/apt/sources.list.d/ directory
       b. search for sbt.list
       c. comment the https://dl.bintray.com/sbt/debian/Packages line.

Step 3:
 install sbt manually.

above steps applicable for any type of package.