使用Masonry时出现
[LayoutConstraints] Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't want.
Try this:
(1) look at each constraint and try to figure out which you don't expect;
(2) find the code that added the unwanted constraint or constraints and fix it.
至于解决方案，就是对view内部使用Masonry布局的空间添加布局优先级，就可以移除这些警告了。
例如：
[self.backgroundImageView mas_makeConstraints:^(MASConstraintMaker*make){make.edges.equalTo(self);}];
修改为：
[self.backgroundImageView mas_makeConstraints:^(MASConstraintMaker*make){make.edges.equalTo(self).priorityHigh();}];
