Error with function: arcpy.mp.CreateWebLayerSSDraft
Hi,
Here is the code that I used, I hope it helps you resolve your issue! Note that I replaced the actual username and password with XXXX. I am a beginner in Python but if you have questions I'll do my best to help 
"Public_lac" is my map in my ArcGIS Pro Projet. Since I have many maps in my project I had to find wich "number" was associated to "Public_lac" because I could not call the map by name so this is the line: mp = prj.listMaps("Public_lac")[0] .
##Upload - overwrite Public_lac
import arcpy
import os, sys
from arcgis.gis import GIS
##Start setting variables
#Set path to the project
prjPath = "C:\\Users\\Proprio\\Desktop\\ArcGISOnline_FichierTravail\\AppWeb_ZecsQuébec.aprx"
#Feature service/SD name in arcgis.com, user/password of the owner account
sd_fs_name= "Public_lac"
portal = "http://www.arcgis.com"
user = "XXXX"
password = "XXXX"
# Set sharing options
shrOrg = True
shrEveryone = True
shrGroups = ""
### End setting variables
# Local paths to create temporary content
relPath = 'C:\\Users\\Proprio\\Documents\\ArcGIS\\Projects'
sddraft = os.path.join(relPath, "WebUpdate.sddraft")
sd = os.path.join(relPath, "WebUpdate.sd")
# Create a new SDDraft and stage to SD
print("Creating SD file")
arcpy.env.overwriteOutput = True
prj = arcpy.mp.ArcGISProject(prjPath)
mp = prj.listMaps("Public_lac")[0]
arcpy.mp.CreateWebLayerSDDraft(mp, sddraft, sd_fs_name, 'MY_HOSTED_SERVICES', 'FEATURE_ACCESS','', True, True)
arcpy.StageService_server(sddraft, sd)
print("Connecting to {}".format(portal))
gis = GIS(portal, user, password)
# Find the SD, update it, publish /w overwrite and set sharing and metadata
print("Search for original SD on portal...")
sdItem = gis.content.search("{} AND owner:{}".format(sd_fs_name, user), item_type="Service Definition")[0]
print("Found SD: {}, ID: {} \n Uploading and overwriting...".format(sdItem.title, sdItem.id))
sdItem.update(data=sd)
print("Overwriting existing feature service...")
fs = sdItem.publish(overwrite=True)
if shrOrg or shrEveryone or shrGroups:
print("Setting sharing options...")
fs.share(org=shrOrg, everyone=shrEveryone, groups=shrGroups)
print("Finished updating: {} - ID: {}".format(fs.title, fs.id))
We have an automated process that overwrites a hosted feature layer in ArcGIS Online, like the blog post referenced above. We encountered an issue somewhere around February 4, 2019 involving a RuntimeError exception in the call to arcpy.mp.CreateWebLayerSDDraft() that prints out nothing meaningful when handled in a try/except.
The portion of the code that was failing is as follows...
try: arcpy.mp.CreateWebLayerSDDraft(map_or_layers=arcpro_map, out_sddraft=sd_draft_filename, service_name="Elected_Officials", server_type="MY_HOSTED_SERVICES", service_type="FEATURE_ACCESS", folder_name="MD Elect", overwrite_existing_service=True, copy_data_to_server=True, enable_editing=False, allow_exporting=False, enable_sync=False, summary=None, tags=None, description=None, credits=None, use_limitations=None) except RuntimeError as rte: print(f"Runtime Error: {rte}") exit() else: arcpy.StageService_server(in_service_definition_draft=sd_draft_filename, out_service_definition=sd_filename)
Outside of a try/except this is the error output...
File "C:\Program Files\ArcGIS\Pro\Resources\ArcPy\arcpy\mp.py", line 105, in CreateWebLayerSDDraft
return _convertArcObjectToPythonObject(arcgisscripting._mapping.CreateWebLayerSDDraft(*_gp_fixargs([map_or_layers, out_sddraft, service_name, server_type, service_type, folder_name, overwrite_existing_service, copy_data_to_server, enable_editing, allow_exporting, enable_sync, summary, tags, description, credits, use_limitations], True)))
RuntimeError
After much trial and error we figured out that the space in the folder name value was causing the issue. The process had been running for months with no issue using the string value "MD Elect". It looks like something in the underlying arcpy code was changed. We revised our ArcGIS Online folder name to eliminate the space, so that the destination folder matched the string we were forced to pass, and gave the function "MD_Elect" and the process runs again. We also tried "MD%20Elect", thinking it might be some web related issue, even though the function of interest doesn't make a web call, but it failed with the RuntimeError. The default of None and also a blank string "" worked, as a side note.
So, for our anonymous RuntimeError exception thrown by arcpy.mp.CreateWeblayerSDDraft the solution was to eliminate spaces in the string value passed to the folder_name keyword parameter.