As explained in the Performance Assistant error description, solution is to maintain the fiscal year dependent version.
In order to do so, either use the link provided in the description, go directly to transaction OKEV, or, in SPRO, open Controlling > General Controlling > Organization > Maintain versions
Here, the starting point might be (depending on how you opened the transaction) to give the Controlling Area.
Then, select the version that has to be maintained – in current example, version 0
Double click on Settings for Each Fiscal Year – and, from there, on New Entries
Enter the Fiscal Year needed, 2017 here, and save
A customizing request will be necessary to proceed
And that’s it, data should be saved – the Purchase Order creation can proceed