Issue explicit error on shim failure

[garthk]

If shimming child_process, dns, fs, net etc:

• shimAliases passes undefined to generateFileBasedModuleName
• … which passes it to getModuleFullRootName
• … which tries to call path.split despite path being undefined

The root cause is shimming the un-shimmable. Troubleshooting would be easier if shimAliases' reducer did something like:

const shim = shims.fileShims[x];
assert.notEqual(shim, undefined, `no shim available for ${x}`);
const mod = generateFileBasedModuleName(shim);

I can submit a PR for that if someone can confirm my theory about what's going on, here. I haven't yet given Brunch explicit instructions on how to behave. It strikes me it's inhaling my server-side modules as if they're client side.

[goshacmd]

Thanks for the report! The way to fix is to simply skip these shims as no alias is needed for these, because brunch will shim them to {} anyway.

I submitted https://github.com/brunch/deppack/pull/11 to address this.