user.rb

# :facepalm:

class User < ActiveRecord::Base
  validate do |user|
    if user.login.blank?
      user.errors.add_to_base("User Name can't be blank")
    else
      user.errors.add_to_base("User Name is too short(Minimum is 3 characters)") if user.login.length<3 and user.login.length !=0 
      user.errors.add_to_base("User Name is too long(Maximum is 3 characters)") if user.login.length>40
      user.errors.add_to_base("User Name has already been taken.") if User.find_by_login(user.login)
    end 
  end 
end

The worst thing is that two lines above from that there are calls to validates_uniqueness_of and validates_presence_of :P