Thanks for your replies otavioschwanck and CorvusRuber .Before following your suggestions i ran the install command again this evening and gets raven reader installed.
~ $ sudo snap install raven-reader
Password:
2019-04-07T17:47:14+05:30 INFO Waiting for restart...
Warning: /snap/bin was not found in your $PATH. If you've not restarted your
session since you installed snapd, try doing that. Please see
https://forum.snapcraft.io/t/9469 for more details.
raven-reader 0.4.4 from Meet Godhani (mrgodhani) installed
~ $
Despite the warning Raven shows in the 'other' category of budgie menu and works.Thanks again.
Edit: After system restart raven stops to open through menu or terminal.And i removed it.Peace of mind!