Hopefully fix Windows tests

- Error codes are different
- Match fs.mkdir behavior on Windows when creating root

lib/mkdirs/__tests__/issue-93.test.js

@@ -24,12 +24,12 @@ describe('mkdirp: issue-93, win32, when drive does not exist, it should return a
   it('should return a cleaner error than inifinite loop, stack crash', done => {
     const file = 'R:\\afasd\\afaff\\fdfd' // hopefully drive 'r' does not exist on appveyor
     fse.mkdirp(file, err => {
-      assert.strictEqual(err.code, 'ENOENT')
+      assert.strictEqual(err.code, 'EPERM')
 
       try {
         fse.mkdirsSync(file)
       } catch (err) {
-        assert.strictEqual(err.code, 'ENOENT')
+        assert.strictEqual(err.code, 'EPERM')
       }
 
       done()

lib/mkdirs/__tests__/root.test.js

@@ -8,17 +8,17 @@ const assert = require('assert')
 /* global describe, it */
 
 describe('mkdirp / root', () => {
-  // '/' on unix, 'c:/' on windows.
+  // '/' on unix
   const dir = path.normalize(path.resolve(path.sep)).toLowerCase()
 
-  // if not 'c:\\' or 'd:\\', it's probably a network mounted drive, this fails then. TODO: investigate
-  if (process.platform === 'win32' && (dir.indexOf('c:\\') === -1) && (dir.indexOf('d:\\') === -1)) return
+  // Windows does not have permission to mkdir on root
+  if (process.platform === 'win32') return
 
   it('should', done => {
     fse.mkdirp(dir, 0o755, err => {
-      if (err) throw err
+      if (err) return done(err)
       fs.stat(dir, (er, stat) => {
-        if (er) throw er
+        if (er) return done(er)
         assert.ok(stat.isDirectory(), 'target is a directory')
         done()
       })