Ensure package exists when checking tags

[jajaperson]

Fixes #179

[fregante]

This should probably verify that the error contains is not in the npm registry. so it doesn't hide all errors

[jajaperson]

@bfred-it Okay, I'll do that.

[jajaperson]

🤦‍♂️ okay should work now.

[sindresorhus]

The output of the command on error is:

{
  "error": {
    "code": "E404",
    "summary": "'sdfsdfagsdagag' is not in the npm registry.\nYou should bug the author to publish it\n(or use the name yourself!)\n\nNote that you can also install from a\ntarball, folder, http url, or git url.",
    "detail": "\n 'sdfsdfagsdagag@latest' is not in the npm registry.\nYour package name is not valid, because \n 1. name can only contain URL-friendly characters\n\nNote that you can also install from a\ntarball, folder, http url, or git url."
  }
}

I think it would be better to just check the code property instead on relying on the error summary being stable.

[sindresorhus]

@jajaperson Please write a descriptive PR title.

[jajaperson]

*bfred-it