Check if all necessary / recommended executables are installed.

def check_executables():
    """Check if all necessary / recommended executables are installed."""
    print("\033[1mCheck executables\033[0m")
    required_executables = [utils.get_nntoolkit()]
    for executable in required_executables:
        path = which(executable)
        if path is None:
            print("%s ... %sNOT%s found" % (executable, Bcolors.WARNING,
                                            Bcolors.ENDC))
        else:
            print("%s ... %sfound%s at %s" % (executable, Bcolors.OKGREEN,
                                              Bcolors.ENDC, path))