ArcPy - Find duplicate Field Aliases within MXD

FindDuplicateFieldAliases.py

import arcpy, os

os.system('cls')

mxd = arcpy.mapping.MapDocument(r"\\Server\Share\MyMap.mxd")
tolerateFieldWhenDisabled = True

for layer in arcpy.mapping.ListLayers(mxd):
    print "Checking Layer '" + layer.name + "'"

    if not layer.isFeatureLayer:
        print "Layer '" + layer.name + "' is no feature layer"
        continue
    
    layerDescription = arcpy.Describe(layer)
    fieldInfo = layerDescription.fieldInfo

    distinctAliasNames = []

    # unfortunately, this script does not work
    # when using ListFields(), the initially used SDE connection has to be present to
    # retrieve the feature class.
    # when using layerDescription, no aliases will be returned
    #
    # see here for more http://desktop.arcgis.com/en/arcmap/10.3/analyze/arcpy-mapping/layer-class.htm
    # => field alias of MXD is not supported, so the SDE file HAS TO EXIST
    fields = arcpy.ListFields(layer.dataSource)
    ##fields = layerDescription.fields
                   
    for field in fields:
        print field
        aliasName = field.aliasName

        if aliasName not in distinctAliasNames:
            distinctAliasNames.append(aliasName)
        else:
            if tolerateFieldWhenDisabled == True:
                fieldIndex = fieldInfo.findFieldByName(aliasName)
                visibility = fieldInfo.getVisible(fieldIndex)

                if visibility == "VISIBLE":
                    raise Exception("Layer '" + layer.name + "' contains duplicate field alias '" + aliasName + "'")
            else:
                raise Exception("Layer '" + layer.name + "' contains duplicate field alias '" + aliasName + "'")    

print "Completed"