unify usage message

unqar.py

@@ -31,20 +31,25 @@ def __del__(self):
  self.file.close()
 
 
-if len(sys.argv) < 2:
+def print_usage():
  print("Usage: %s <qar file> [<output path>]" % sys.argv[0])
+
+
+if len(sys.argv) < 2:
+ print_usage()
  exit(1)
 
 binaryReader = BinaryReader(sys.argv[1])
 output_path = pathlib.Path.cwd()
+
 if len(sys.argv) > 2:
  output_path = str(sys.argv[2])
 
 try:
  magic = binaryReader.unpack('<H') # 71 02
  if magic != 0x0271:
  print("Not a supported qar file.")
- print("Usage: %s <qar file>" % sys.argv[0])
+ print_usage()
  exit(2)
  file_count = binaryReader.unpack('<H')
  print("Going to extract %d files." % file_count)