.bundle/cache/compact_index/rubygems.org error

I got this in few months, and can't find the solution.
after all, I found it. Just clean the cache. 
 
http://stackoverflow.com/questions/41472374/bundle-install-fails-permission-denied-rb-sysopen

rm -rf ~/.bundle/cache

There was an error while trying to write to
`/home/xxx/.bundle/cache/compact_index/rubygems.org.443.29b0360b937aa4d161703e6160654e47/versions`. It is likely that you need to
grant write permissions for that path.