[Error] Issues with creating a new type of weather

[Seenit45]

I want to implement a new type of weather in my game. I've made a new move for it and have also created the script for the new type of weather to appear inbattle.
Here are some of the scripts that I had to modify:

PBWeather

#11045744
begin
  module PBWeather
    SUNNYDAY    = 1
    RAINDANCE   = 2
    SANDSTORM   = 3
    HAIL        = 4
    HARSHSUN    = 5
    HEAVYRAIN   = 6
    STRONGWINDS = 7
    BLACKSKY    = 9  #Made it number 9 because 8 was taken by Shadow Sky
    # Shadow Sky is weather 8
  end

rescue Exception
  if $!.is_a?(SystemExit) || "#{$!.class}"=="Reset"
    raise $!
  end
end

PokeBattle_Battle

if @weather==PBWeather::SUNNYDAY
      pbCommonAnimation("Sunny",nil,nil)
      pbDisplay(_INTL("The sunlight is strong."))
    elsif @weather==PBWeather::BLACKSKY
      pbCommonAnimation("Darkness",nil,nil)
      pbDisplay(_INTL("It is pitch black."))

when PBWeather::BLACKSKY
      @weatherduration=@weatherduration-1 if @weatherduration>0
      if @weatherduration==0
        pbDisplay(_INTL("The darkness faded away."))
        @weather=0
        PBDebug.log("[End of effect]")        
      else
        pbCommonAnimation("Darkness",nil,nil)
#        pbDisplay(_INTL("The battlefield is covered in darkness."))
      end

PokeBattle_MoveEffects

lass PokeBattle_Move_159 < PokeBattle_Move
  def pbEffect(attacker,opponent,hitnum=0,alltargets=nil,showanimation=true)
    case @battle.weather
    when PBWeather::HEAVYRAIN
      @battle.pbDisplay(_INTL("There is no relief from this heavy rain!"))
      return -1
    when PBWeather::HARSHSUN
      @battle.pbDisplay(_INTL("The extremely harsh sunlight was not lessened at all!"))
      return -1
    when PBWeather::STRONGWINDS
      @battle.pbDisplay(_INTL("The mysterious air current blows on regardless!"))
      return -1
    when PBWeather::SUNNYDAY
      @battle.pbDisplay(_INTL("But it failed!"))
      return -1
    end
    pbShowAnimation(@id,attacker,nil,hitnum,alltargets,showanimation)
    @battle.weather=PBWeather::BLACKSKY
    @battle.weatherduration=5
    @battle.weatherduration=8 if attacker.hasWorkingItem(:HEATROCK)
    @battle.pbCommonAnimation("Darkness",nil,nil)
    @battle.pbDisplay(_INTL("The battlefield was engulfed in darkness!"))
    return 0
  end
end

PField_Weather

begin 
    module PBFieldWeather
    None        = 0 # None must be 0 (preset RMXP weather)
    Rain        = 1 # Rain must be 1 (preset RMXP weather)
    Storm       = 2 # Storm must be 2 (preset RMXP weather)
    Snow        = 3 # Snow must be 3 (preset RMXP weather)
    Blizzard    = 4
    Sandstorm   = 5
    HeavyRain   = 6
    Sun = Sunny = 7
    Darkness    = 8

The problem is that when I try to run the game, I keep getting a SyntaxError. The main issue from the "when PBWeather::BLACKSKY" from PokeBattle_Battle. I really don't know what it is, since I've been following the instructions I found on the Essentials Wiki. Does anyone know what's wrong?

 

[Maruno]

Try posting the whole method containing the line that causes the problem.