title: Can't find python executable with node-gyp rebuild when installing with npm
body: <p>Hello I'm getting the following error when I try to install prerequisites to compile with sass:</p>
  
  <pre><code>$ npm install
  
  &gt; iltorb@1.0.13 install c:\gitrepo\PORT_BDL_BOOTSTRAP\node_modules\iltorb
  &gt; node-gyp rebuild
  
  c:\gitrepo\PORT_BDL_BOOTSTRAP\node_modules\iltorb&gt;if not defined npm_config_node_gyp (node "C:\Users\CTH\Desktop\bazar\nodejs\node\node_modules\npm\bin\node-gyp-bin\\..\..\node_modules\node-gyp\bin\node-gyp.js" rebuild )
    else (node "" rebuild )
  gyp ERR! configure error
  gyp ERR! stack Error: Can't find Python executable "python", you can set the PYTHON env variable.
  gyp ERR! stack     at failNoPython (C:\Users\CTH\Desktop\bazar\nodejs\node\node_modules\npm\node_modules\node-gyp\lib\configure.js:449:14)
  gyp ERR! stack     at C:\Users\CTH\Desktop\bazar\nodejs\node\node_modules\npm\node_modules\node-gyp\lib\configure.js:404:11
  gyp ERR! stack     at C:\Users\CTH\Desktop\bazar\nodejs\node\node_modules\npm\node_modules\graceful-fs\polyfills.js:264:29
  gyp ERR! stack     at FSReqWrap.oncomplete (fs.js:82:15)
  gyp ERR! System Windows_NT 6.1.7601
  gyp ERR! command "c:\\Users\\CTH\\Desktop\\bazar\\nodejs\\node\\node.exe" "C:\\Users\\CTH\\Desktop\\bazar\\nodejs\\node\\node_modules\\npm\\node_modules\\node-gyp\\bin\\node-gyp.js" "rebuild"
  gyp ERR! cwd c:\gitrepo\PORT_BDL_BOOTSTRAP\node_modules\iltorb
  gyp ERR! node -v v5.6.0
  gyp ERR! node-gyp -v v3.4.0
  gyp ERR! not ok
  bootstrap@4.0.0-alpha.5 c:\gitrepo\PORT_BDL_BOOTSTRAP
  `-- grunt-contrib-compress@1.4.1
    `-- lodash@4.17.4
  
  npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@^1.0.0 (node_modules\chokidar\node_modules\fsevents):
  npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.0.17: wanted {"os":"darwin","arch":"any"} (current: {"os":"win32","arch":"x64"})
  npm WARN optional SKIPPING OPTIONAL DEPENDENCY: iltorb@1.0.13 (node_modules\iltorb):
  npm WARN optional SKIPPING OPTIONAL DEPENDENCY: iltorb@1.0.13 install: `node-gyp rebuild`
  npm WARN optional SKIPPING OPTIONAL DEPENDENCY: Exit status 1
  </code></pre>
  
  <p>I've set the PYTHON and PYTHONPATH variables, that doesn't change anything. The problem is related to node-gyp rebuild that doesn't work probably due to my python executable. I use a python portable version for windows could it be related to that ?</p>
  
  <p>I've tried also this without success:</p>
  
  <pre><code>npm config set python C:\Users\CTH\Desktop\bazar\python\App\python.exe
  </code></pre>