自动布局 Autolayout 报错：Unable to simultaneously satisfy constraints.

在使用自动布局时，不断的报下面的错误：

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. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints) 
(
    "<NSLayoutConstraint:0x8c67c10 V:[UIButton:0x8c67320]-(2)-|   (Names: '|':UIView:0x8c65ad0 )>",
    "<NSAutoresizingMaskLayoutConstraint:0x8e166b0 h=--& v=--& UIButton:0x8c67320.midY ==>",
    "<NSAutoresizingMaskLayoutConstraint:0x8e166e0 h=--& v=--& V:[UIButton:0x8c67320(0)]>",
    "<NSAutoresizingMaskLayoutConstraint:0x8e130d0 h=-&- v=-&- UIView:0x8c65ad0.height == PicCollectionViewCell:0x8c65a00.height>",
    "<NSLayoutConstraint:0x8e13710 'UIView-Encapsulated-Layout-Height' V:[PicCollectionViewCell:0x8c65a00(100)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x8c67c10 V:[UIButton:0x8c67320]-(2)-|   (Names: '|':UIView:0x8c65ad0 )>

Break on objc_exception_throw to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.

这种错误，一般就两个原因：1，你的约束的确设置错误；2，忘记设置控件的：setTranslatesAutoresizingMaskIntoConstraints 等于NO 。

我就属于第二种情况，其实错误信息里也写的很清楚了，NSAutoresizingMaskLayoutConstraint:0x8e166e0 。