title: Can't run python script in sublime text 3 because build (CTRL+B) not working
body: <p>i installed sublime text3 and tried to run a python code in it.
  when i choose <code>python</code> from <code>Build system</code> and tried to run the code i got this error :</p>
  
  <blockquote>
    <p>'python' is not recognized as an internal or external command,
    operable program or batch file. [Finished in 0.1s with exit code 1]
    [shell_cmd: python -u "C:\Python26\Lib\py\try66.py"] [dir:
    C:\Python26\Lib\py] [path: C:\Program Files (x86)\Common
    Files\Intel\Shared
    Files\cpp\bin\Intel64;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0\;C:\Program
    Files (x86)\Skype\Phone\;C:\Program Files
    (x86)\AMD\ATI.ACE\Core-Static;C:\Program Files (x86)\Microsoft SQL
    Server\100\Tools\Binn\;C:\Program Files\Microsoft SQL
    Server\100\Tools\Binn\;C:\Program Files\Microsoft SQL
    Server\100\DTS\Binn]</p>
  </blockquote>
  
  <p>so i installed <code>sublimeREPL</code> file and set the path in the file.
  and the i create a new Build system named <code>python26repl.sublime-build</code> with this context:</p>
  
  <pre><code>&gt; { "target": "run_existing_window_command", "id":  "repl_python_run",
  &gt; "file": "config/Python/Main.sublime-menu" }
  </code></pre>
  
  <p>and i set the <code>Build system</code> to <code>python26repl.sublime-build</code>. now <code>Build</code> (CTRL+B) doesn't work.i mean they do nothing  but save the code.
  please help, what's the problem? how to fix?</p>