Set the 'errno' and 'code' of a module when not found.

[TooTallNate]

I'm not sure if you guys will take this one, but basically I'm currently sniffing "not find" from the error object's message, which is rather hacky. So checking this property is a little cleaner approach.

Example of what I'm talking about:
https://github.com/TooTallNate/node-weak/blob/1781429d8590eaf70c7fe64d87dbc642af6d1e1d/lib/bindings.js#L13

[felixge]

-1 on this particular solution.

Setting err.code to ENOENT does not allow to differentiate between the module not being found, vs. the module doing something like this:

fs.readFileSync('does-not-exist.json');

I would propose setting err.code to 'MODULE_NOT_FOUND' and making it part of the official module loading API (by that I mean documenting it).

[TooTallNate]

Good point @felixge, I hadn't considered the case where the module itself throws a similar error. Then in the MODULE_NOT_FOUND case, what should we set the errno to?

[felixge]

errno is deprecated. See #2211 (comment)

I'll submit a patch for the docs mentioning that, as well as a patch for the master branch to remove the remaining errno properties.

[TooTallNate]

Ok nice sounds good, I'll update this pull with the 'MODULE_NOT_FOUND' code, and tests and docs.

[TooTallNate]

@felixge Ok fixed up with your suggestions. Thanks!
@ry @bnoordhuis @isaacs or any of the other committers have any thoughts?

[TooTallNate]

@koichik Thanks for the suggestions; they've been implemented. Test passes. This pull should be ready.

[koichik]

@TooTallNate Thanks, merged in 3f987cd, ec11525, and 855f466.