'Returns the python version in Vim as a string, e.g. \'2.7\''

def launch(self, config=[]):

    pid_file = self.name_temp('vim.pid')
    done_file = self.name_temp('loading_done')
    if os.path.exists(done_file):
        os.remove(done_file)
    post_config = []
    post_config.append(('%s    <<    EOF' % ('py3' if PYTHON3 else 'py')))
    post_config.append('import    vim,    sys')
    post_config.append(("with    open('%s',    'w')    as    pid_file:    pid_file.write(vim.eval('getpid()'))" % pid_file))
    post_config.append(("with    open('%s',    'w')    as    done_file:" % done_file))
    post_config.append("                done_file.write('%i.%i.%i'    %    sys.version_info[:3])")
    post_config.append('EOF')
    config_path = self.write_temp('vim_config.vim', textwrap.dedent((os.linesep.join((config + post_config)) + '\n')))
    self.send_to_terminal(('    NVIM_LISTEN_ADDRESS=/tmp/nvim    %s    -u    %s\r\n' % (self._vim_executable, config_path)))
    wait_until_file_exists(done_file)
    self._vim_pid = int(read_text_file(pid_file))
    return read_text_file(done_file).strip()
