Typically when you see an EPERM error that is caused by the OS. You can find quite a bit about it on Google and Stack Overflow. Typically users experience that issue on windows that have their drives indexed. Although, I want to believe that the npm client is your issue, I have a feeling that something is happening first and then the EPERM error is happening on the cleanup of the file. Especially since you are saying that npmjs.org does not have the problem. I noticed at the end of the error, it says "A complete log of the run exists at", would you be able to send that over to us?
If you don't feel comfortable attaching that to this post, you can send it to support@inedo.com and put [Support QA-609] in the subject. Just please let me know that you emailed it so I can keep an eye out for the email.
Thanks,
Rich
