loadNodeModules() should be more clear about what went wrong

I had an error loading a library, but all it told me is that it couldn’t resolve the module. That’s fine, but the real issue is that the package’s main file didn’t exist.

Here’s some payload information:

{ x: 'snabbdom-view',
  start: '/Users/krainboltgreene/Code/krainboltgreene/deushack/source/client/cycle',
  dirs: [] }

We can definitely make this better. We can say all the directories we looked in, what exact file we;'re looking for (in this case main) and then do some reading to show the user that it’s the package;'s fault.

[krainboltgreene]

As the maintainer of a big project i feel that.

[ljharb]

@krainboltgreene yes, potentially - there are tools that rely on the exact string and type of an error that resolve throws in specific situations. I’ve broken angular-cli and ember-cli before by changing an error message, and am not anxious to repeat it.