I was able to solve this using the [answer from @AlexTereshenkov][1] to arrive at this workflow.

 1. In the Project pane of ArcGIS Pro 1.3.1 I right-clicked on the enterprise database connection under Databases to open its Properties
 2. I copied its Name e.g. `N:\path\SDEfiles\TEST PROD [personal].sde` (`SDEfiles` is simply a folder that I created to place `*.sde` files into)
 3. Ran this test which printed `Polygon` and worked without error:


----------


    import arcpy
    rock_unit_table = r"N:\path\SDEfiles\TEST PROD [personal].sde\Test.TEST.DETAILED_SURFACE_COMP"
    print(arcpy.Describe(rock_unit_table).shapeType)
    arcpy.MakeFeatureLayer_management(rock_unit_table, "rockUnit_lyr")

  [1]: http://gis.stackexchange.com/a/236296/115