Try python launcher when stock python is python 3.

Consult the python launcher when the python on the path is python 3.
If a python 2 exists on the system, it will tell us.

Fixes: nodejs#987
PR-URL: nodejs#992
Reviewed-By: Johan Bergström <bugs@bergstroem.nu>

lib/configure.js

@@ -343,6 +343,7 @@ function PythonFinder(python, callback) {
 }
 
 PythonFinder.prototype = {
+  checkPythonLauncherDepth: 0,
   env: process.env,
   execFile: cp.execFile,
   log: log,
@@ -386,6 +387,8 @@ PythonFinder.prototype = {
   // executable for "execFile", we have to use the launcher to figure out
   // where the actual "python.exe" executable is located.
   checkPythonLauncher: function checkPythonLauncher () {
+    this.checkPythonLauncherDepth += 1
+
     this.log.verbose(
         'could not find "' + this.python + '". checking python launcher')
     var env = extend({}, this.env)
@@ -395,13 +398,14 @@ PythonFinder.prototype = {
     this.execFile('py.exe', launcherArgs, { env: env }, function (err, stdout) {
       if (err) {
         this.guessPython()
-        return
+      } else {
+        this.python = stdout.trim()
+        this.log.verbose('check python launcher',
+                         'python executable found: %j',
+                         this.python)
+        this.checkPythonVersion()
       }
-      this.python = stdout.trim()
-      this.log.verbose('check python launcher',
-                       'python executable found: %j',
-                       this.python)
-      this.checkPythonVersion()
+      this.checkPythonLauncherDepth -= 1
     }.bind(this))
   },
 
@@ -435,6 +439,8 @@ PythonFinder.prototype = {
       }
       if (valid) {
         this.callback(null, this.python)
+      } else if (this.win && this.checkPythonLauncherDepth === 0) {
+        this.checkPythonLauncher()
       } else {
         this.failPythonVersion(version)
       }

test/test-find-python.js

@@ -195,6 +195,77 @@ test('find python - no python, use python launcher', function (t) {
   }
 })
 
+test('find python - python 3, use python launcher', function (t) {
+  t.plan(10)
+
+  var f = new TestPythonFinder('python', done)
+  f.env = {}
+  f.win = true
+
+  f.which = function(program, cb) {
+    t.strictEqual(program, 'python')
+    cb(null, program)
+  }
+  f.execFile = function(program, args, opts, cb) {
+    f.execFile = function(program, args, opts, cb) {
+      f.execFile = function(program, args, opts, cb) {
+        t.strictEqual(program, 'Z:\\snake.exe')
+        t.ok(/import platform/.test(args[1]))
+        cb(null, '2.7.0')
+      }
+      t.strictEqual(program, 'py.exe')
+      t.notEqual(args.indexOf('-2'), -1)
+      t.notEqual(args.indexOf('-c'), -1)
+      cb(null, 'Z:\\snake.exe')
+    }
+    t.strictEqual(program, 'python')
+    t.ok(/import platform/.test(args[1]))
+    cb(null, '3.0.0')
+  }
+  f.checkPython()
+
+  function done(err, python) {
+    t.strictEqual(err, null)
+    t.strictEqual(python, 'Z:\\snake.exe')
+  }
+})
+
+test('find python - python 3, use python launcher, python 2 too old',
+     function (t) {
+  t.plan(9)
+
+  var f = new TestPythonFinder('python', done)
+  f.checkedPythonLauncher = false
+  f.env = {}
+  f.win = true
+
+  f.which = function(program, cb) {
+    t.strictEqual(program, 'python')
+    cb(null, program)
+  }
+  f.execFile = function(program, args, opts, cb) {
+    f.execFile = function(program, args, opts, cb) {
+      f.execFile = function(program, args, opts, cb) {
+        t.strictEqual(program, 'Z:\\snake.exe')
+        t.ok(/import platform/.test(args[1]))
+        cb(null, '2.3.4')
+      }
+      t.strictEqual(program, 'py.exe')
+      t.notEqual(args.indexOf('-2'), -1)
+      t.notEqual(args.indexOf('-c'), -1)
+      cb(null, 'Z:\\snake.exe')
+    }
+    t.strictEqual(program, 'python')
+    t.ok(/import platform/.test(args[1]))
+    cb(null, '3.0.0')
+  }
+  f.checkPython()
+
+  function done(err, python) {
+    t.ok(/is not supported by gyp/.test(err))
+  }
+})
+
 test('find python - no python, no python launcher, good guess', function (t) {
   t.plan(6)