Ran into this issue today, using the DEM Reconditioning tool from the ArcHydro toolbox.
Output path is: C:\Users\sxxxxx.sxxxxx\Desktop\tempgis\tempras.gdb\AgreeDEM
Error is:
374: Failed to execute. Parameters are not valid.
ERROR 010818: The output path contains spaces.
Failed to execute (EucAllocation).
('line 290', 'c:\\program files\\arcgis\\pro\\Resources\\ArcToolbox\\Scripts\\ArcHydro\\demreconditioning.py', '')