I am getting error  http client 403 where I have deployed google cloud function using python to download the daily clamav virus definitions from http://database.clamav.net.

ClamAV have implemented rate-limiting and restrictions because some people were downloading updates far too frequently from AWS and Google Cloud servers.

See: https://lists.clamav.net/pipermail/clamav-users/2021-March/010559.html

You should use FreshClam to download the updates. If you are running a private mirror, then use this tool to refresh your mirror: https://github.com/micahsnyder/cvdupdate

-- 
Paul
Paul Smith Computer Services
support@pscs.co.uk - 01484 855800