Editor throws "get_dataPath is not allowed to be called from a script constructor" error on upgrading project from 2018.2 to 2018.3.0a7

Steps to Reproduce:
1. Import "The Courtyard" from the Asset Store to 2018.2.0f2
2. Close the project and open it with 2018.3.0a7
3. Open "Courtyard" scene
4. Enter Play mode.

Reproduced with:
2018.3.0a7

Not reproduced with:
2018.3.0a6.

Error Details:
UnityException: get_dataPath is not allowed to be called from a script constructor (or instance field initializer). Called from 'SubstanceImporter'.
See "Script Serialization" page in the Unity Manual for further details.
Substance.Game.NativeCallbacks.InitSubstance ()
Substance.Game.SubstanceMain.Initialize ()
Substance.Editor.SubstanceImporter..ctor ()