Filters out duplicate user

app/controllers/courses_controller.rb

@@ -798,6 +798,7 @@ def categorize_courses_for_listing(courses)
   def write_cuds(cuds)
     rowNum = 0
     rosterErrors = {}
+    rosterWarnings = {}
     rowCUDs = []
     duplicates = Set.new
 
@@ -863,7 +864,7 @@ def write_cuds(cuds)
         new_cud.delete(:year)
 
         # Build cud
-        if !user.nil?
+        if !user.nil? && !existing
           cud = @course.course_user_data.new
           cud.user = user
           params = ActionController::Parameters.new(
@@ -945,11 +946,11 @@ def write_cuds(cuds)
     rowCUDs.each do |cud|
       next unless duplicates.include?(cud[:email])
 
-      msg = "Validation failed: Duplicate email #{cud[:email]}"
-      if !rosterErrors.key?(msg)
-        rosterErrors[msg] = []
+      msg = "Warning : Duplicate email #{cud[:email]}"
+      if !rosterWarnings.key?(msg)
+        rosterWarnings[msg] = []
       end
-      rosterErrors[msg].push(cud)
+      rosterWarnings[msg].push(cud)
     end
 
     return if rosterErrors.empty?