How to reproduce:
1. Create a new project in Unity 2017.1.1p4 and open the Asset Store window
2. Search for Standard Assets in the Asset Store and download them
3. Create a new project in Unity 5.6.0f3 and open the Asset Store window
4. Search for Standard Assets in Asset Store, note that the package is already downloaded and thus the option to Import (instead of Downloading) is already present
5. Import the Standard Assets

Expected result: Asset Store should manage Asset Versions for each Unity Version and download/import the appropriate version. In this case, Asset Store could detect that newer Standard Assets version was downloaded before and thus prevent user from importing, before downloading the proper version
Actual result: Asset Store imported the Unity 2017.1.1p4 version of Standard Assets into Unity 5.6.0f3 resulting into errors in the Console

Note: Issue can be fixed by manually downloading Standard Assets again in the Asset Store Downloads, but this is confusing to Asset Store customers, especially the new ones