This doesn't appear to have been fixed at 2.0.1 unless the "patch" is a separate download. The following runs fine as a logged in user, but fails when run as other user -> service account. The same service account has been successfully triggering 2.7 scripts for years, so it's not an OS permission issue. Never had any of these required to be authenticated to a Portal issues with 2.7, it's not clear why authentication to a Portal is required in 3.5.3 just to import a library.
C:\Users\sasquatch>"C:\Program Files\ArcGIS\Pro\bin\Python\envs\arcgispro-py3\p
ython.exe" C:\PRODUCTION\GRSM_DISTURBANCE\DISTURBANCE\Maps\ArcGIS\UPDATE_GRSM_DI
STURBANCE_PRO.py
Traceback (most recent call last):
File "C:\PRODUCTION\GRSM_DISTURBANCE\DISTURBANCE\Maps\ArcGIS\UPDATE_GRSM_DISTU
RBANCE_PRO.py", line 1, in <module>
import arcpy
File "C:\Program Files\ArcGIS\Pro\Resources\ArcPy\arcpy\__init__.py", line 66,
in <module>
from arcpy.geoprocessing import gp
File "C:\Program Files\ArcGIS\Pro\Resources\ArcPy\arcpy\geoprocessing\__init__
.py", line 14, in <module>
from ._base import *
File "C:\Program Files\ArcGIS\Pro\Resources\ArcPy\arcpy\geoprocessing\_base.py
", line 14, in <module>
import arcgisscripting
RuntimeError: Not signed into Portal.
