Creating new ArcSDE version with ArcPy?

Question

The following script creates a new version in SDE but generates the following error below. Am I missing an environment?

# Name: SDE_CreateVersion
# Description: Creates a new SDE version

# Import system modules
import os
import arcpy

# Set local variables
sdeConnection = "Database Connections\Jordan.sde"
parentVersion = "sde.DEFAULT"
versionName = os.environ.get( "USERNAME" )

for version in arcpy.da.ListVersions(sdeConnection):
    if version.name.split(".")[0] == versionName:
        break
    else:
        # Execute CreateVersion
        arcpy.CreateVersion_management(sdeConnection, parentVersion, versionName, "PUBLIC")

This is the error produced:

Traceback (most recent call last):
  File "C:\Users\jnmiller\Desktop\Create Version.py", line 20, in <module>
    arcpy.CreateVersion_management(sdeConnection, parentVersion, versionName, "PUBLIC")
  File "C:\Program Files (x86)\ArcGIS\Desktop10.6\ArcPy\arcpy\management.py", line 18856, in CreateVersion
    raise e
ExecuteError: ERROR 001148: Cannot create a version with the specified name.
Failed to execute (CreateVersion).