Alter display code to pad with spaces and simplify

VendServer/VendingMachine.py

@@ -160,9 +160,9 @@ class VendingMachine:
 		return (code == '501', code, string)
 
 	def display(self, string):
-		if len(string) > 10:
-			string = string[0:10]
-		self.wfh.write('D'+string+'\n')
+		# display first ten characters of string, left aligned
+		self.wfh.write('D%-10.10s\n' % string)
+
 		(code, string) = self.get_response()
 		return (code == '300', code, string)