After updating to the latest Unity version (5.4.3f1, released 17th of November 2016) I get this error with P4Connect:
get_dataPath is not allowed to be called from a ScriptableObject constructor (or instance field initializer), call it in OnEnable instead. Called from ScriptableObject 'Config'.
See "Script Serialization" page in the Unity Manual for further details.
This bug has been fixed with release 2017.1 available on ftp now:
ftp://ftp.perforce.com/perforce/r17.1/bin.multiarch/p4Connect.unitypackage