def METHOD_NAME(executable):
    """
    Search executable in PATH environment. Return path if found, None if not.
    """
    path = os.environ.get('PATH')
    if not path:
        return
    for p in path.split(os.path.pathsep):
        p = os.path.join(p, executable)
        if os.path.exists(p):
            return p
        p += '.exe'
        if os.path.exists(p):
            return p