尝试调用这个方法：
avatarIconImageView.setContentHuggingPriority(UILayoutPriorityDefaultLow,forAxis: UILayoutConstraintAxis.Horizontal)
并捕获此异常：
Undefined symbols for architecture armv7:
“_UILayoutPriorityDefaultLow”,referenced from:
__TFC13TCProject_iOS36TCAvatarWithCounterUniversalCellView22configureBodyCellViewsfS0_FT_T_
in TCAvatarUniversalCellView.o ld: symbol(s) not found for
architecture armv7 clang: error: linker command Failed with exit code
1 (use -v to see invocation)
这是什么意思？
