Reproduction steps:
1) Download and open attached project
2) Press Build and run
-- Notice that build fails with errors:

Error: Error while saving blame file, build will continue
Error: The prefix "tools" for attribute "tools:overrideLibrary" associated with an element type "uses-sdk" is not bound.

UnityEditor.HostView:OnGUI()

and

AndroidSDKToolsException: Unable to merge android manifests. See the Console for more details.
UnityEditor.Android.AndroidSDKTools.DetectErrorsAndWarnings (System.String logMessages, System.String errorMsg)
UnityEditor.Android.AndroidSDKTools.RunCommandInternal (System.String javaExe, System.String sdkToolsDir, System.String[] sdkToolCommand, Int32 memoryMB, <...> (full error pasted in edit section)

Note: This reproduces only with 26.0.1 and 26.0.2 (currently newest) versions of sdk tools

Reproduced with:
2017.2.0b1, 2017.1.0f1, 5.6.1p2, 5.5.4p1, 5.4.5p3

RESOLUTION: WONTFIX. The issue is caused by a bug in the project. Specifically, Assets/Plugins/Android/AndroidManifest.xml is invalid and broken. The exact issue is that the manifest lacks xmlns:tools="http://schemas.android.com/tools" namespace declaration and thus the new manifest merger tool from 26.0.2 fails to merge it with another manifest (specifically support-v4-25.2.0.aar), which uses the tools XML namespace.