Use pathlib in test_user_car

tilde-train.py

@@ -37,12 +37,12 @@
 from random import shuffle ## allowing us to randomize selection of cars.
 import glob  ## allowing us to search the file system for .choochoo files.
 import sys ## so we can read command line arguments.
-import getpass ## so we can get the user's username
 import curses
 from signal import signal, SIGINT
 import time ## allowing the loop steps of train animation to be slowed
 import string ## for input validation
 from inspect import cleandoc
+from pathlib import Path
 
 traincarFN = ".choochoo"
 max_x = 35  ## max length of train car.
@@ -122,16 +122,15 @@ def print_help():
 
 
 def test_user_car():
-  username = getpass.getuser()
-  fname = "/home/" + username + "/" + traincarFN
+  fname = Path.home() / traincarFN
   try:
-    myfile =  open(fname, 'r')
-  except:
-    print("ERROR: Couldn't open " + fname)
-    print("Either it doesn't exist, or is not readble by the tilde.train script.")
-    sys.exit(1)
+    choochoo_string = fname.read_text("utf-8")
+  except OSError as err:
+    raise OSError(
+      f"Couldn't open {fname}\n"
+      "Either it doesn't exist, or is not readble by the tilde.train script."
+    ) from err
 
-  choochoo_string = myfile.read()
   choochoo_list = choochoo_string.split("\n")
 
   car = "\n".join(choochoo_list)
@@ -177,17 +176,14 @@ def test_user_car():
   if train_height > max_y+1:
     print("FAIL. Your train car is too tall.")
     print("It should be no taller than " + str(max_y) + " lines in height.")
-    myfile.close()
     sys.exit(1)
 
   if train_length > max_x:
     print("FAIL. Your train car is too long.")
     print("It should be no longer than " + str(max_x) + " characters in length.")
-    myfile.close()
     sys.exit(1)
 
   print("PASS. Your train car will work on the tilde.town tracks! :)")
-  myfile.close()
   sys.exit()
 
 def link_car(car):