What is the point of the GKT dependency?
Looking at the code.. it does nothing.

If there is no point to this package, I think it should be removed from the dependency list.
Noticed due to troubles during install due to SSL inspection / resigning. Able to work around by upgrading to latest NPM. Looks like others have had issues due to this as well. (e.g.
w/ NPM v4.x
npm ERR! fetch failed https://tgz.pm2.io/gkt-1.0.0.tgz
npm WARN retry will retry, error on last attempt: Error: unable to get local issuer certificate
npm ERR! fetch failed https://tgz.pm2.io/gkt-1.0.0.tgz
npm WARN retry will retry, error on last attempt: Error: unable to get local issuer certificate
w/ NPM v5.0.1
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: gkt@https://tgz.pm2.io/gkt-1.0.0.tgz (node_modules/pm2/node_modules/gkt):
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: request to https://tgz.pm2.io/gkt-1.0.0.tgz failed, reason: unable to get local issuer certificate
We already answered on few issues actually but anyway : it's a optional dependency that is used for analytics purpose.
I wasn't able to reproduce your problem (with both npm 4 & 5) but i restart the application that handle this request, is it fixed for you ?
Issue on my end due to ssl inspection from the firewall. Issue would be difficult to reproduce elsewhere.
Will try later and update.
Sadly i can't help you otherwise, you can just use npm install -g pm2 --no-optional but it may still break on older npm version due to the fact that the flag isn't working properly.
It's broken again.
[2019-11-06 09:04:22] npm http fetch GET 403 https://tgz.pm2.io/gkt-1.0.0.tgz 122ms
It totally sucks! Please remove it.
Go install the latest pm2 version