src: remove uv errno

This commit attempts to take care of a TODO reported in issue 4641.
I'm not sure if just removing errno is an option, as there might be
code that is depending on this errno being availble. If it cannot be
removed perhaps the TODO can. Hopefully feedback on this commit will
sort that out.

Refs: nodejs#4641

src/node.cc

@@ -940,9 +940,6 @@ Local<Value> UVException(Isolate* isolate,
 
   Local<Object> e = Exception::Error(js_msg)->ToObject(isolate);
 
-  // TODO(piscisaureus) errno should probably go; the user has no way of
-  // knowing which uv errno value maps to which error.
-  e->Set(env->errno_string(), Integer::New(isolate, errorno));
   e->Set(env->code_string(), js_code);
   e->Set(env->syscall_string(), js_syscall);
   if (!js_path.IsEmpty())

test/parallel/test-domain-implicit-fs.js

@@ -36,7 +36,6 @@ d.on('error', common.mustCall(function(er) {
   assert.ok(!er.domainEmitter);
   assert.strictEqual(er.code, 'ENOENT');
   assert.ok(/\bthis file does not exist\b/i.test(er.path));
-  assert.strictEqual(typeof er.errno, 'number');
 }));
 
 

test/parallel/test-domain.js

@@ -77,12 +77,10 @@ d.on('error', function(er) {
       assert.ok(!er.domainEmitter);
       assert.strictEqual(er.code, 'ENOENT');
       assert.strictEqual(er_path, 'this file does not exist');
-      assert.strictEqual(typeof er.errno, 'number');
       break;
 
     case
     "ENOENT: no such file or directory, open 'stream for nonexistent file'":
-      assert.strictEqual(typeof er.errno, 'number');
       assert.strictEqual(er.code, 'ENOENT');
       assert.strictEqual(er_path, 'stream for nonexistent file');
       assert.strictEqual(er.domain, d);