That wouldn't have been so bad,e_____ that he had a couple of wmpty bottles in his back poxkers.

except
except that在这里的意思是但是、可惜之意，后面跟的句子是实际已经发生的事。

except that 除了...之外, 只可惜

That wouldn't have been so bad 本来不会那么糟的……
这句话用了虚拟语气，表示跟事实不相符。

except

except that
除了...之外, 只可惜

eg：
I would do it with pleasure, except that I am too busy.
（要不是我太忙了，我会很高兴去做的。）

I would buy the suit, except that it costs too much.
如果不是它售价太高的话，我本想买下那件衣服