Raise if auth is unsuccessful

db/scrape.rb

     @first = first
     @last = last
     @log = log
-    @cookie = login(ENV['VLV_USERNAME'], ENV['VLV_PASSWORD'])
+
+    authenticate!
   end
 
   def scrape
     end
   end
 
+  private
+
+  def authenticate!
+    @cookie = login(ENV['VLV_USERNAME'], ENV['VLV_PASSWORD'])
+
+    raise "Error logging into VLV. Check your credentials." if @cookie.nil?
+  end
+
   def scrape_thread(t)
     log t[:title]