Resolved versions for app (26.1.0) and test app (27.1.1) differ

最近新建项目gradle编译会出现如下错误：

Error:Execution failed for task ':app:preDebugAndroidTestBuild'.
Conflict with dependency 'com.android.support:support-annotations' in project ':app'. 
Resolved versions for app (26.1.0) and test app (27.1.1) differ. 
See https://d.android.com/r/tools/test-apk-dependency-conflicts.html for details.

大意是主模块app和test app模块所依赖的com.android.support:support-annotations包版本不一样，但是我的build.gradle中设置的只有26.1.0版本，实在不知27.1.1是哪来的。没关系：只要在build.gradle中加上下面一行代码强制将所有com.android.support:support-annotations依赖包的版本设置为26.1.0即可：

configurations.all { resolutionStrategy.force 'com.android.support:support-annotations:26.1.0' }